How tempo changes affect audio clips

When you change the tempo of a project that contains audio, Sonar allows you to automatically stretch or shrink audio clips to follow the changed tempo. Otherwise, the MIDI tracks will speed up or slow down while the audio tracks will play at the same speed.

When you change the tempo of your project, audio clips that have stretching enabled change tempo along with the project, while those that do not have stretching enabled do not. Audio clips that do not have stretching enabled change in size when moved to a part of your project that has a different tempo.

In some situations you may not want to adjust the speed of your audio:

If your project contains background music and a voice-over, you might want to change the tempo of the background music without altering the voice-over.

If you’re trying to modify the speed of some MIDI tracks to match a sampled drum groove, you want to leave the audio unchanged.

An audio clip’s Time Base property determines what happens to the clip’s start time when you change the project tempo. You specify the time base in the Clip Properties Inspector’s Properties section (see Properties Inspector - Clip Properties and Properties section). The two Time Base options are as follows:

Musical (M:B:T). If the clip is set to the Musical time base, the clip’s M:B:T position stays constant, and its Absolute (SMPTE) position shifts.

Absolute (SMPTE). If the clip is set to the Absolute (SMPTE) time base, its Absolute position stays constant, and its M:B:T position shifts.

Note: The length of a clip may also change when you change the tempo—audio clips maintain their absolute (SMPTE) length, while a MIDI clip will follow the value in the Time Base field.

Syncing audio and the project tempo

If you record without a metronome or import an audio recording, the audio will most likely not align perfectly to the project’s tempo (measure and beat grid). You can set the initial project tempo to match the recording as closely as possible, but the tempo will likely drift over time due to human performance variations and imperfections.

There are two ways to sync the audio recording and project tempo:

Conform the audio to the project tempo. With this solution you stretch the audio so it follows the project tempo. For details, see Configuring audio clips to follow tempo changes.

Conform the project tempo to the audio. With this solution you create a tempo map that matches the audio. The metronome click will perfectly follow along with the audio. Use this solution if you want to retain the recorded human performance variations. For details, see Setting the project tempo from an audio recording.

Configuring audio clips to follow tempo changes

If you want audio clips to follow tempo changes, configure the clips to follow tempo changes before you change the project tempo. An audio clip can use either AudioSnap or Groove Clip stretching to follow tempo changes:

Method 1 (AudioSnap):

1.	Select the audio clip(s) that you want to follow the project tempo.

2.	Press ALT+A to open the AudioSnap palette.

3.	Click the Clip Follows Project Tempo button on the AudioSnap palette.

The clip(s) displays the Auto Stretch icon , and is synchronized to the project’s tempo map (including future tempo changes). The drop-down list lets you specify at which resolution the clip should follow tempo changes. The options are as follows:

Beats

Measures

Clip (default)

Auto Stretch

Note: The Clips follow project tempo command only works on clips that are configured to use musical time (the Time Base property is set to Musical in the Clip Properties Inspector).

Note: If the audio clip does not play back at the expected tempo, the clip might not have an accurate internal tempo map. For details about editing a clip’s tempo map, see Editing a clip’s tempo map.

Figure 102. AudioSnap palette

Alternatively, you can enable Follow Project Tempo in the Clip Properties Inspector:

1.	Select the audio clip(s) that you want to follow the project tempo.

2.	In the Clip Properties Inspector’s AudioSnap section, select Enable, then select Follow Project Tempo.

3.	Under Follow Options, specify at which resolution the clip should follow tempo changes:

Beats

Measures

Clip (default)

Auto Stretch

For details, see Synchronizing audio and the project tempo and Changing a project’s tempo.

Figure 103. Clip Properties Inspector.

For more information about AudioSnap, see AudioSnap.

Method 2 (Groove Clip):

1.	Select the audio clip(s) that you want to follow the project tempo.

2.	In the Clip Properties Inspector’s Groove Clip section, select Stretch to Tempo.

The audio clips stretch or shrink to fit the project’s tempo. Sonar uses the Beats in Clip and Original Tempo parameters to make the change.

Audio clips that do not have Stretch to Tempo enabled change in size when moved to a part of your project that has a different tempo.

For details, see Properties Inspector - Clip Properties and Groove Clip section.

Figure 104. Clip Properties Inspector.

For more information about Groove clips, see Working with Groove Clip audio and To set the tempo of a Groove Clip.

 

See:

How tempo changes affect automation

Tempo track

Tempo Inspector

Changing tempos

Using the Tempo track

Using the Tempo Inspector

Using the Transport module

Using the Tempo commands

Setting the project tempo by tapping

Offsetting the tempo map

Setting the project tempo from an audio recording

Setting the project tempo from freely recorded MIDI or audio

Aligning measure/beat boundaries manually

Setting the Metronome and Tempo settings

Backwards compatibility

Tempo