3. An Overview of the Mixxx Interface
Welcome to the Mixxx interface. This is where the magic happens. You are going to want to get very familiar with this interface because it is the main way to use Mixxx. In this chapter, we present the default interface of Mixxx and describe its elements, knobs and faders.
This is the Latenight skin. It is the default skin supplied with Mixxx. There are a variety of others skins included with Mixxx. You should explore them all to figure out which one you prefer. This section will focus on Latenight only.
3.1. The Deck Sections
The deck section allows you to control everything relating to a virtual turntable deck. We are going to break this down into sections.
3.1.1. Track Information Display
- Track Title
The title of the track that was loaded into a deck is displayed on top. This is the same as the title listed under the Title column heading in the Mixxx library. This information is initially loaded from the track’s metadata. If the metadata is missing, the title and artist are guessed from the filename.
- Track Artist
The artist of the track is listed below. It is the same as listed under the Artist column heading in the Mixxx library.
- BPM (Tempo)
The number at the top right is the effective BPM of the track. This is the detected BPM of the track, adjusted for the playback rate of the track. For example, if the track is normally 100 BPM, and it is playing at +5%, then the effective BPM will read 105 BPM.
Dica
You can use a keyboard shortcut and tap with the beat to set the BPM to the speed you are tapping, go to Using a Keyboard for more information.
Time Elapsed/Remaining/Both
Novo na versão 2.1.0: Option to show elapsed and remaining time simultaneously
By default it displays the total elapsed time in the track up to the millisecond. Clicking on the display switches to the Time Remaining view, which indicates how much time is left before the track reaches the end. Clicking the display again, both the elapsed and remaining time are shown simultaneously in the format elapsed time / remaining time. You can change the default in
.
3.1.2. Waveform Displays
The waveform section of a deck allows you to visualize the audio changes that occur throughout the track, you can basically “see” your music.
By default the waveform displays are aligned parallel to each other in order to make beatmatching easier, as it is possible to beatmatch visually by aligning the beats that appear in each waveform.
Depending on the skin Mixxx displays either parallel waveforms (default) or separate waveforms. Select your preferred appearance in
.Aviso
If you have a slower computer and notice performance issues with Mixxx, try lowering the frame rate or changing the waveform type in
.- Waveform summary
The big waveform summary shows the waveform envelope of the track near the current playback position and is updated in real time. The mouse can be used on the waveform to pause, scratch, spin-back or throw the tracks. Right-clicking on the waveforms allows you to drag with the mouse to make temporary pitch adjustments.
Dica
You can select from different types of displays for the waveform, which differ primarily in the level of detail shown in the waveform, in
.
Waveform overview
Novo na versão 2.1.0: Darken played part of track in decks and samplers
The smaller, zoomed-out version of the waveform shows the various markers within the track as well as the waveform envelope of the entire track. This is useful because they allow DJs to see breakdowns far in advance. As visual aid, the part of the track that has already been played is darkened.
Clicking somewhere on the waveform allows you to jump to an arbitrary position in the track. Like with the Waveform summary, you can select from different types of displays for the overview in
.
- Vinyl Widget
The line on the vinyl widget rotates if the track moves. It is similar to the position marker found on scratch records. Use the mouse on the vinyl widget to pause, scratch, spin-back or throw tracks - just like a real record. When performing Loop rolls or right-clicking on the vinyl during playback, a “ghost” marker hints where the playback will continue. The Vinyl Widget is hidden by default and can be enabled in the Deck Options Button Grid.
If Vinyl control is enabled, it can optionally display the time-coded vinyl signal quality. Activate the option in .
- Waveform Zoom
Using the mouse-wheel everywhere in the waveform summary will zoom the waveform in or out. You can choose whether to synchronize the zoom level between the decks in
.- Waveform Marker
While mixing, various additional markers can appear on the waveforms:
Position marker: The static vertical line in the center of the waveform summary indicates the playback point of the deck. The waveform overview includes a vertical line to show the current position within the track.
Beat marker: The regular white lines on the waveform summary indicate the locations of beats in the audio, also called the beatgrid.
Cue marker: Indicates the position of the cue point.
Hotcue marker: Indicate the position and number of a hotcue point if set.
Loop-in/Out marker: Indicate the beginning and the end of a loop.
Loop overlay: Is drawn between the Loop-in/Out markers and changes color depending on whether a loop is activated or not.
Track ending notification: If the waveform overview flashes red, only 30 seconds are left before the track reaches the end.
3.1.4. Playback/Cue Controls
- Play/Pause Button
Clicking the Play/Pause button starts and pauses the playback.
Veja também
The actual behavior of the Play/Pause button depends on the selected Cue mode.
Dica
To return to the beginning of the track, right-click on the deck’s Fast-Rewind Button.
- Cue Button
If the button is pressed while the track is playing, the play position jumps to the Cue point on the track and the track is paused. Once the track is paused at the Cue point, you can preview it by holding the Cue Button. If you have not moved the Cue point yet, the default point is at the track’s beginning.
Veja também
The actual behavior of the Cue button depends on the selected Cue mode.
3.1.4.1. Setting Cue points
Every track has a Cue point, by default on its beginning. Unlike with Hotcues, you can’t delete, but only move Cue points.
The Cue point is moved according to the selected Cue mode, as explained below.
3.1.4.2. Auto Cue
Mixxx automatically seeks to the saved Cue point on track load. If none exists, seeks to the beginning of the track.
Uncheck
to always seek to the beginning of the track.3.1.4.3. Using Cue Modes
Mixxx supports various Cue modes that adapt to fit other devices in your setup, or your personal preferences. The actual behavior of the Play, Pause, and Cue buttons depends on the selected Cue mode. To change the Cue mode, go to
.Mixxx mode (default)
While paused at Cue point (Cue button lit):
Holding down the Cue button plays the track from the Cue point, as long as the button is pressed. After releasing the Cue button, the track jumps back to Cue point and pauses again. Continue playback by pressing the Play/Pause button before releasing the Cue button.
While paused not at Cue point (Cue button flashing):
Tapping the Cue button stores the current position as new Cue point.
While playing:
Tapping the Cue button causes the track to instantly jump to the location of the Cue point where it pauses the playback.
Tapping the Play/Pause button pauses the track at the current position.
Mixxx mode (no blinking)
Is the same as the default Mixxx mode, but with no blinking indicators.
Pioneer mode
It is basically the same as Mixxx mode but the buttons are more flashy like a Pioneer CDJ player.
The Play/Pause button flashes once per second when a track is paused.
The Cue button flashes twice a second when the next push will move the Cue point.
Denon mode
While paused at Cue point (Cue button lit):
Holding down the Cue button plays the track from the Cue point, as long as the button is pressed. After releasing the Cue button, the track jumps back to Cue point and pauses again. Continue playback by pressing the Play/Pause button before releasing the Cue button.
Tapping the Play/Pause button starts the track at the current position.
While paused not at Cue point (Play button flashing):
Tapping the Cue button moves the track back to Cue point.
Tab the Play/Pause button to start playing. The Cue point moves to the position where the track was started.
While playing:
Tapping the Cue button causes the track to instantly jump to the location of the cue point where it pauses the playback.
Tapping the Play/Pause button pauses the track at the current position.
Numark mode
It is basically the same as Denon mode but without a flashing Play/Pause button.
This mode is useful if you want to implement a custom skin with 3-button decks, featuring a Cue button, a dedicated Pause button, and a Play/Stutter button.
CUP (Cue + Play) mode
While paused at Cue point (Cue button lit):
Continue playback by releasing the Cue button.
While paused not at Cue point (Cue button flashing):
Tapping the Cue button stores the current position as new Cue point. Continue playback by releasing the Cue button.
While playing:
Tapping the Cue button causes the track to instantly jump to the location of the Cue point where it pauses the playback. Continue playback by releasing the Cue button.
Tapping the Play/Pause button pauses the track at the current position.
Dica
Use the Hotcue Controls to place more reference points on a track.
Veja também
You can also use keyboard shortcuts for Cueing. Go to Using a Keyboard for more information.
3.1.5. Transport Controls
- Fast-Rewind button
As long as the button is pressed, the track will play in reverse with increased speed. Right-clicking on the button will seek the play position to the beginning of the track.
- Fast-Forward button
As long as the button is pressed, the track will play with increased speed. Right-clicking on the button will seek the play position to the end of the track.
- Reverse button
As the name suggests, this button plays a track backwards. Right-clicking on the button puts a track into reverse while being held, resumes the track and disables Slip mode when released. Useful to censor expletives on the fly, or simply as part of your mix.
3.1.6. Vinyl Control Mode and Cueing controls
The control above the waveforms relate to the vinyl control feature in Mixxx and is hidden in the default Mixxx user interface. Click the VINYL section expansion button in the mixer section, or use the specific Application shortcuts to show or hide the section.
Abs/Rel/Const button
Absolute mode: The track position equals needle position and speed.
Relative mode: The track speed equals needle speed regardless of needle position.
Constant mode: The track speed equals last known-steady speed regardless of needle input.
Off/One/Hot button
This button determines how cue points are treated in vinyl control relative mode:
Off: Cue points are ignored.
One Cue: If the needle is dropped after the cue point, the track will seek to that cue point.
Hot Cue: The track will seek to nearest previous hotcue point.
Veja também
For more information on how to use Vinyl control in your setup, go to the chapter Controlo Vinilo.
3.1.7. Sync and Rate Controls
The rate controls allow you to change the rate at which tracks are played. This is very useful for beatmatching two tracks together in a mix. You can control rate changes also from your computer’s keyboard, see the chapter Using a Keyboard for more information.
SYNC button
Left-Click: Changes the rate of the track so that the BPM and phase of the track matches the other deck.
Right-Click: Only changes the rate of the track to match the other deck but does not adjust the phase.
Decks and samplers now pick which sync target to sync to on the fly. Decks can’t sync to samplers and samplers can only sync to decks. The sync target for samplers is:
The first deck (in numerical order) that is playing a track with a detected beatgrid, and has a rate different than zero.
The first deck (in numerical order) that has a track loaded with a detected beatgrid, no matter if it is playing or stopped.
So basically, if you sync a sampler and both deck 1 and deck 2 are playing a track with a beatgrid then deck 1 will win since numerically it is first. The sync targets for decks are chosen with the new master sync feature, see Master Sync for more information.
- Pitch/Rate slider
The slider allows you to change the speed of the song, by default up to 10% from the tracks original tempos. The speed will increase as you move the slider up, opposite to the behavior found on DJ turntables and CDJ. Right-clicking on the slider will reset the tempo to its original value.
- Pitch Rate Display
The percent that the track’s rate is sped up or slowed down is noted here. Is the Pitch/Rate slider positioned at the center, the pitch rate display is at +0.0%, which indicates no change.
- Pitch/Rate buttons
The plus and minus buttons increase or decrease the tempo in steps at which a song is played, same as pulling the pitch slider slightly. By right-clicking the buttons you get even finer adjustments.
- Temporary Pitch/Rate buttons (Nudge)
Pushing the left and right arrow buttons is like nudging the metal edge of a turntable, or the outer edge of a CD player. It will give the track a push or pull forwards or backwards. If the buttons are released the previous tempo is restored. The buttons can act as either a fixed pitch bend or a ramping pitch bend.
Veja também
To customize the amount by which the buttons alter the pitch of the track, the slider range as well as the direction, go to
.Dica
If the tempo of a track changes, you’ll notice that the tone changes based on the pitch used (e.g. playing at faster pitch gives a chipmunk sound). You can enable the Keylock feature to maintain a constant tone.
3.1.8. Loop Controls
In this section of the Mixxx interface you can control (beat-)loops and set the loop points of a track.
Beatlooping Buttons
Instant loop: The numbered buttons represents a different bar length. Clicking on any of that buttons will set a loop of the defined number of beats from the beat immediately following the current playback position. If a loop is set, a loop overlay will be drawn on the waveforms.
Loop roll: Right-click on any of the numbered loop buttons to temporarily setup a rolling loop over the defined number of beats. Playback will resume where the track would have been if it had not entered the loop.
Double loop: Clicking on the plus button will double the current loop’s length up to 64 bars. The length of the loop overlay in the waveform will increase accordingly.
Halve loop: Clicking on the minus button will halve the current loop’s length down to 1/32 bars. The length of the loop overlay in the waveform will decrease accordingly.
Loop Buttons
Loop-In: This button allow you to manually set the start point of a loop. A loop-in marker is placed on the waveform indicating the position. If clicked when a loop was already set, it moves the start point of a loop to a new position.
Loop-Out: This button allow you to manually set the end point of a loop. A loop-out marker is placed on the waveform indicating the position. If clicked when a loop was already set, it moves the end point of a loop to a new position.
Loop: Also dubbed Reloop, this button toggles whether the loop is active or not. This works for manually placed loops as well as automatic loops set by the beatlooping buttons. Depending on the current status of the loop, the loop overlay on the waveforms changes color.
Dica
If you are playing inside a loop and want to move the end point beyond its current position in the track, click on the Loop button first and when the play position reaches the desired position, click on the Loop-Out button.
Veja também
If the Quantize mode is enabled, the loops will automatically snap to the nearest beat. This is disabled by default, click on the Quantize Mode Toggle to enable it.
3.1.9. Hotcue Controls
To jump in between different parts of a track, you can use these numbered buttons. You can also use keyboard shortcuts, go to Using a Keyboard for more information.
3.1.9.1. Setting Hotcues
Clicking on a numbered button will set a hotcue at the current play position on the track. A marker with the corresponding number will appear in the waveform and the button will light up to indicate that the hotcue is set.
3.1.9.2. Playing Hotcues
While playing: Tap a hotcue button to cause the track to instantly jump to the location of the hotcue and continue playing. If you are playing inside a loop and tap a hotcue whose position is outside of the loop, then the track still instantly jumps to the hotcue but the loop will be deactivated.
While stopped: Tap a hotcue button to cause the track to instantly jump to the location of the hotcue and start playing as long as the button is pressed. Press the Play keyboard shortcut while the hotcue button is pressed to continue playback, then release the hotcue button.
3.1.9.3. Hotcue labels
Novo na versão 2.1.0.
You can add custom names to hotcues. Right-clicking on a selected track in the track list reveals the context menu. Choose and add a label for the hotcue. Press Enter , then click OK to save.
The hotcue indicator on the waveform changes to the format #:label
.
3.1.9.4. Deleting Hotcues
To delete a hotcue, right-click on the numbered button. The marker in the waveform will be deleted as well.
Nota
Mixxx supports up to 36 hotcues per deck. By default, only some of them are visible in the user interface. You can customize your keyboard or controller mappings to use all of them.
Veja também
Just as with the loops (see above), if the quantize mode is enabled, the hotcues will automatically snap to the nearest beat. This is disabled by default, click on the Quantize Mode Toggle to enable it.
3.2. The Mixer Section
The mixer section of the Mixxx user interface allows you to control how the different decks and samplers are mixed together.
3.2.1. Channel Faders and Level Meters
- Level meters
In the center of the mixer section are 4 level meters. The two outer-most level meters are for each deck, while the 2 inner-most level meters are the left and right level meters for the master output. These should stay at the top of the green region, with the loudest parts of the music (transients) briefly going into the yellow region. They should never be in the red region. Refer to Setting your levels properly (gain staging) for more details.
- Line faders
The two large faders on either side of the level meters are the deck volume faders, also known as Channel- or Line-faders. Adjusting these controls the volume of each deck.
Dica
Some DJ’s prefer to use the line faders over the crossfader for fading between tracks. Try it, you may like it.
3.2.3. Headphone and Master Mix Controls
- Pre/Main Knob
Allows you to control how much of the master output you hear in the Headphones output. It works like a crossfader between the stereo Master and stereo PFL signal. If the knob is set to the left, you only hear the PFL signal, which is the usual position for prelistening tracks.
This can be used to practice DJing with only one stereo output and a set of either speakers or headphones.
Additionally, this can be used to mix in headphones when you cannot hear the speakers connected to the Master output and there are no booth monitor speakers. Some DJs prefer to use this knob to mix in headphones all the time, but many find it to be a difficult way to play. If there is only one set of speakers and no booth monitors, you can avoid the need to mix in headphones by setting up the speakers behind you so both you and your audience can hear them.
Nota
Don’t forget to activate the PFL button on the deck you want to listen to in your headphones.
- Head-Split Button
If activated, two mono signals are sent to the headphone output instead of one stereo signal. The master signal plays in the right channel, while the cueing signal plays in the left channel. You can still adjust the Pre/Main Knob to control the mix of the master and cue signals in the left channel.
- Balance Knob
This knob allows you to adjust the balance (left/right orientation) of the master output.
- Master Knob
The Master Gain Knob controls the gain applied to the Master output signal that Mixxx sends to your sound card, Internet broadcasting servers, and recorded mixes. Generally, this knob should not be adjusted. To change the output volume, a gain control should be adjusted as close to the speakers as possible for the best signal-to-noise ratio throughout your signal chain. Ideally, the volume would only be adjusted by adjusting the gain on the power amplifier. On active speakers, including computer speakers, studio monitors, and PA systems that do not require a separate amplifier, this means adjusting the gain on the speakers (which may be labeled «Volume»).
As a DJ, you may not have access to the power amplifier. In that case, adjust the volume by adjusting the gain on the equipment closest to the power amplifier that you have access to. Typically, this is a DJ mixer. If you are not going through a mixer, adjust the gain of your sound card. If your sound card does not have any controls on it (for example, for sound cards built into computers), adjust the sound card settings with your OS mixer program. The Master Gain Knob in Mixxx should be a last resort for adjusting volume.
Aviso
In no case should any part of the signal chain be clipping, indicated by a level meter going into its red region or an LED labeled «clipping» turning on.
Veja também
For an explanation of why you should set your gains this way, see Setting your levels properly (gain staging).
- Head Gain Knob
This knob controls the gain applied to the headphone output signal that Mixxx sends to your sound card. Generally, this knob should not be adjusted. To adjust the volume in your headphones, adjust your sound card’s gain on the headphone output. Most external sound cards have a gain knob specifically for the headphone jack. If you use an onboard sound card for your headphones, adjust the gain control in your OS mixer program. If your sound card only has one gain knob that controls both the main output and the headphone output, then adjust the Head Gain knob in Mixxx to control the volume of your headphones without affecting your main output.
3.2.5. Equalizers and Gain Knobs
- Gain Knob
The gain knob allows you to adjust the gain applied to the deck. Use this to compensate for the differences in recording levels between tracks. In general, you should adjust this knob so that the track’s level meter stays around the top of the green region with the loudest parts of the track (the transients) briefly going into the yellow region. Do NOT turn the Gain Knob up so much that the level meter is in the red region. At this point the track is clipping, which sounds bad and could damage equipment.
Nota
By default, Mixxx automatically applies an additional ReplayGain so tracks have approximately equal loudness at unity gain. Your tracks must be analyzed to take advantage of this feature. When an unanalyzed track is loaded, Mixxx calculates its ReplayGain value, but will not apply a newly calculated ReplayGain value to a track after it has already started playing (to avoid a sudden change in the gain of a playing track).
Veja também
For an explanation of why you should set your gains this way, see Setting your levels properly (gain staging).
- EQ Knobs
The low, mid, and high EQ knobs allow you to change the filters of the audio. This allows you to selectively reduce or boost certain frequency ranges of the audio.
Aviso
Be careful not to raise the EQs so much that the signal clips, indicated by a level meter being in the red region. See Setting your levels properly (gain staging) for a more detailed explanation.
- Kill Switches
The small boxes next to each EQ knob are called kills. Hold these buttons to fully remove that frequency range. Short click on the buttons for latching. When in Latch mode, click again to restore the frequency range. If the Kill switches do not work as expected, check the high/low shelf EQ settings in the preferences.
Veja também
You can customize the EQ settings in
.3.2.6. Crossfader
The crossfader determines the actual volume of each deck when moving the slider from left to right. If both decks are playing and the crossfader is in its default center position, then you will hear both decks. Right-clicking on the crossfader will reset the slider to its default position.
You can reverse the configuration of the crossfader, so that the right deck is on the left end of the crossfader and vice versa. This is also known as Hamster Style. To adjust the crossfader to your style of mixing, go to
.Dica
Using the AutoDJ feature in Mixxx, you can automate the crossfade between the decks.
3.3. The Sampler Section
Samplers are miniature decks. They allow you to play short samples and jingles but also additional tracks in your mix. They come with a small overview waveform and a limited number of controls. All controls work just like on the regular decks, see The Deck Sections.
The Sampler section can be hidden in the Mixxx user interface. Click the SAMPLER button, or use the specific Application shortcuts to show or hide the section.
3.3.1. Waveform Display
- Waveform overview
The waveform shows the various markers within the track as well as the waveform envelope of the entire track. Clicking somewhere on the waveform allows you to jump to an arbitrary position in the track.
- Waveform Marker
While mixing, some additional markers can appear on the waveforms:
Position marker: A vertical line indicates the playback point of the sample deck.
Hotcue marker: Indicate the position and number of a hotcue point if set.
3.3.2. Track Information Display
- Track Artist/Title
The artist and title of the track that was loaded into a sampler deck is displayed here.
- BPM (Tempo)
The number at the top right is the effective BPM of the track. Tap the BPM to set the BPM to the speed you are tapping.
3.3.3. Deck Options Button Grid
The buttons grid next to the waveform overview allow you to configure the sampler deck. Starting from the top-left and moving counterclockwise the buttons are as follows:
- Repeat Mode Toggle
If enabled, the repeat mode will jump back to the beginning and continue playing when the track finishes.
- Eject Track Button
Clicking this button ejects the track from the deck.
- Mix Orientation Toggle
This control determines the sampler input’s mix orientation.
- Keylock Toggle
Keylock locks the track’s pitch so that adjustments to its tempo via the rate slider do not affect its pitch.
3.3.4. Sample Deck Controls
- Play/Pause button
Clicking the button always starts playback from the cue point. If playback is already enabled the play position will jump back to the cue point. Right-clicking on the button will stop playback and seek the play position to the beginning of the sample.
- Sync Button
Syncs the Sampler deck to a regular deck, as described in Sync and Rate Controls.
Left-Click: Changes the rate of the track so that the BPM and phase of the track matches the sync target.
Right-Click: Only changes the rate of the track to match the sync target but does not adjust the phase.
- Hotcue Controls
To jump in between different parts of a sample, you can use these numbered hotcue buttons.
- PFL/Headphone Button
If active, the pre-fader listen or PFL button allows you to listen to the track in your headphones.
- Gain Knob
Allows you to adjust the gain applied to the track.
- Level Meter
Shows the level of the signal and can be adjusted with the Gain knob.
- Pitch/Rate slider
The slider allows you to change the speed of the sample. Right-clicking on the slider will reset the tempo to its original value.
3.4. The Effects Section
Mixxx comes with some built in sound effects that can be chained together in effect units. Effect units can be freely assigned to different decks as well as other inputs. The buttons for routing decks to effect units are in the The Deck Sections.
Veja também
The Effects chapter has a more detailed explanation of the effects system.
3.5. The Microphone Section
The microphone section is hidden in the default Mixxx user interface. Click the MIC button in the mixer section, or use the specific Application shortcuts to show or hide the section.
Veja também
The Using Microphones chapter has detailed instructions for setting up microphones with various hardware.
3.5.1. Microphone Controls
- Talk Button
Hold this button and talk to mix the microphone input into the Mixxx master output. Short click on the button for latching. This is handy for talking for an extended period, for example when streaming a radio show. When in Latch mode, click again to mute the microphone input.
- Mix Orientation Toggle
This control determines the microphone input’s mix orientation. Either to the left side of crossfader, to the right side or to the center (default). Clicking cycles through all the options.
- Microphone Volume Meter
This displays the microphone volume input signal strength.
- Microphone Gain Knob
Use this knob to adjust the gain of the microphone output. Try to keep the volume at a reasonable level to avoid signal clipping.
3.6. Preview Deck Section
The Preview Deck is a special deck that allows you to pre-listen to tracks in the headphones before using them in your mix. Pre-listening a track does not change the tracks’s Played state as well as the play counter and is not logged in the History. Press CTRL + 4 (Windows/Linux) or CMD + 4 (Mac) to display the Preview Deck.
The features in detail:
Track Artist/Title: The artist and title of the track is displayed here. This is the same listed under the Track and Title column in the Mixxx library. This information is initially loaded from the track’s metadata.
Eject Track button: Clicking this button ejects the track from the deck.
Play/Pause button: Clicking the button starts and pauses the playback. Right-clicking on the button will stop playback and seek the play position to the beginning of the tracks.
Waveform overview: Shows the various markers (Cues, Hotcues) within the track as well as the waveform envelope of the entire track. Clicking somewhere on the waveform allows you to jump to an arbitrary position in the track.
Gain slider: Move the slider to adjust the gain of the track.
Volume Meter: Shows the current volume of the track. If it’s too loud and distorted, a peak indicator flashes red.
Veja também
For more information, go to the chapter Previewing Tracks.