K403/K503 Assignment 6: Digital Performer Audio II

After this assignment, make sure these topics are famliar.

Time-Scaling and Pitch-shifting Audio

Digital Performer lets you change the duration of a soundbite without changing its pitch, and it lets you change the pitch of a soundbite without changing its duration. This is different from the way most samplers work, where transposing a sample also changes its duration.

To time-scale a soundbite, open the Sequence Editor, and move the mouse over either edge of the soundbite — over the colored title bar, not over the waveform display. The cursor changes to a hand.

Click and drag to stretch or shrink the soundbite horizontally. When you release the mouse, Digital Performer creates a new time-scaled sound file, and replaces the soundbite you dragged with one referring to the new sound file. This process takes a moment, during which time the waveform appears hollow, and the soundbite will be silent if you play the sequence.

To pitch-shift a soundbite, select it and choose Transpose from the Region menu. You then see the same window that you would use to transpose MIDI notes. As long as the Transpose audio check box is enabled, the command also affects soundbites.

Don't expect time-scaling by large percentages or transposing by large intervals to sound natural. But sometimes, unnatural is good.

The Spectral Effects menu command combines time-scaling and pitch-shifting with formant-shifting. Go ahead and play with it.

Some extra info about transposition...

Digital Performer has two methods of transposition. The default "PureDSP" method works well for cleanly-recorded, non-reverberant sounds containing a single pitch or melody. (That is, it works for monophonic, not polyphonic, sounds.) This method lets you shift formants independently of pitch, using the Spectral Effects command. The other method does not let you do formant-shifting, but it works better with sound files that are polyphonic or contain reverberation. If the result of the default "PureDSP" transposition sounds garbled, you can arrange for a soundbite to use this alternative method of transposition. This setting is in a pop-up menu in the Info pane of the Soundbites window.

Audio Effects

One of the great things about using audio in Digital Performer is that you can use audio effects. You access the audio effects by choosing them from the insert pop-up menus at the top of each audio track in the Mixing Board window. Most effects have a wet/dry mix control that governs the amount of effect you hear. All effects have a bypass button; toggle this to compare the dry track with the "effected" track.

The best way to get started with effects is to try the presets that most of them include. Select these from the effect window mini-menu. (Access this mini-menu by clicking and holding on the little icon next to the close box for the effect window, shown below.)

A real-time effect assigned to a track affects the track for the entire duration of a sequence. You can apply an effect to a single soundbite by selecting the soundbite and choosing the effect from the Audio > Audio Plug-ins menu. This creates a new soundbite with the effect applied; it leaves the original soundbite alone. This is sometimes a good thing to do, if you want just one soundbite to have an effect but don't want anything else in the track to have the effect. However, you lose the benefits of real-time audio effects: effect-setting automation, easy changing of settings, and chaining of effects.

Automation works for most real-time effect settings. Use it just like the automation of volume and pan: record-enable automation, then change effect settings while playing the sequence. Digital Performer remembers your setting changes. You can edit these in the Sequence Editor the same way you edit volume automation.

Bouncing to Disk

Here's how to get your audio into a form from which you can make audio CDs or MP3s.
  1. Make certain all audio track outputs are set to Analog 1-2.
  2. Select all the audio tracks you want to include in your mix file. Shift-click the track names in the Tracks window to select them. You don't have to include the Master Fader track in the selection. The tracks must be play-enabled.
  3. Use the Start and End time boxes in the Tracks Window to select the time range you want to capture. Usually, you'll want the entire length of your sequence, plus a few extra empty measures to accommodate any reverb or echo ring-off. (A shortcut: to select the entire sequence duration, double-click on the word "Selection" that appears to the left of the Start and End time boxes.)
  4. Choose Bounce to Disk from the Audio menu. Use the following settings in the dialog that appears.

    A new stereo soundbite will appear at the bottom of the Soundbites window. This is the soundbite you'll export in the next section.

Exporting the Stereo Mix File

You now have a stereo mix soundbite that contains the sound of your sequence. This soundbite actually refers to two sound files, because Digital Performer uses split stereo files instead of one interleaved file. Split stereo means that your stereo mix is split into a pair of mono files, with '.L' (left) and '.R' (right) suffixes. Most other software likes to see interleaved stereo files, in which the individual sample numbers for the left and right channels are interleaved: L1, R1, L2, R2, L3, R3, L4, R4, etc.

You must convert your split stereo soundbites into an interleaved stereo file, in order to write your mix to a CD or create an MP3 file. Here's how to convert.

  1. Open the Soundbites window, and click on the name of the stereo mix soundbite to select it.
  2. Choose Export Selected Bites from the Soundbites window mini-menu.
  3. Choose a location for the file (e.g., the Desktop), and set Format to AIFF format. Then press Save.

©2007, John Gibson