Making Tracks: Pitch Doctor

MODIFY MELODIES USING DIGITAL PERFORMER'S PITCH-AUTOMATION TOOLS
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In a me-too world where competing DAWs offer essentially the same features, MOTU Digital Performer (DP) separates itself from the pack with its standout pitch-automation functionality. The two most widely known applications for this type of processing are real-time pitch correction and conversion of audio pitches to MIDI data (used, for example, to double monophonic audio phrases on a virtual instrument).

Another little-known but invaluable application is nondestructive rearranging of musical parts in an audio track. Long after the guitarist has packed up and left the studio, for instance, you can change the notes he played to create a better hook — all in real time and without reaching for the record button. You do that by automating the pitch transposition of individual notes, and I'll show you how in this article (see “Step-by-Step Instructions”).

What's on the Menu?

Before you begin, make sure PureDSP file analysis is enabled by navigating to Digital Performer→Preferences→Background Processing and selecting Analyze Soundfiles For DSP As Soon As Possible. Also activate DP's automatic plug-in latency compensation by selecting it under Setup→Configure Audio System→Configure Studio Settings.

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FIG. 1: Choosing Use PureDSP Pitch Shift for a sound bite''s Transpose setting will yield the most-natural-sounding results when automating pitch transpositions.

In the Soundbites window's Info pane, confirm that Use PureDSP Pitch Shift is the Transpose setting for the sound bites you plan to transpose (see Fig. 1). This is the default setting and will produce the most-natural-sounding results.

Now you're ready to tweak your guitar melody. First, in DP's Sequence Editor select the sound bites whose pitches you want to modify. Then choose the pitch mode for the sound bites by selecting Audio→Audio Pitch Correction→Set Pitch Mode For Selected Bites→Instrument. (Had your signal source been a singer, you would have chosen Vocals for the pitch mode.) Don't select Audio→Audio Pitch Correction→Set Track Pitch Mode, because this command will not affect sound bites that have already been recorded.

Next, choose Pitch in the track's track-layer menu. This action displays the blue pitch curve and green pitch segments superimposed over the waveforms of the sound bites. If you can't see the pitch curve, zoom in until it appears. You can move the pitch curve to a position above or below the waveforms by dragging the scroll handle in the track's Pitch ruler, which is located just to the left of the track's graphic display.

If the number of pitch segments is different from the number of notes played, increase or decrease the number of segments until there is one segment per note. A simple way to do this is to select the track, choose Audio→Audio Pitch Correction→Adjust Pitch Segmentation, and, in the window that appears, move the Pitch Separation slider to the right or left to increase or decrease the number of pitch segments.

Alternatively, you can click between two adjacent segments (spanning one musical note) with the Mute tool to join them together into one segment. Clicking on a pitch segment with the Scissor tool will split it into two segments.

Now for the creative part. Click-and-drag a pitch segment up or down to transpose the associated note's pitch in the same direction in half-step increments (see Web Clips 1 and 2). The note will maintain its intonation relative to concert pitch, remaining sharp or flat. To shift the pitch of any note in increments less than a half step, Command-drag its associated pitch segment up or down as needed. To move any note to its pitch center (so that it is neither sharp nor flat), select its pitch segment and choose Audio→Audio Pitch Correction→Quantize Pitch. If you want to revert an edited note to its original pitch, simply select its pitch segment and press the Delete key.

Sheer Genius or Garbage?

Because DP's pitch automation is applied nondestructively and in real time, you can bypass the automation on the affected track at any time during playback in order to compare your new melody with the original (see Web Clip 3). Toggle the P button at the bottom of the track's Pitch ruler to alternately bypass and activate pitch automation. To temporarily defeat pitch automation for one sound bite, open the Soundbites window's Info pane and choose Don't Pitch Shift for that sound bite's Transpose setting.

Once you're happy with your new melody, you may want to make it permanent by selecting any pitch-edited sound bites and choosing Audio→Merge Soundbites. Alternatively, bounce the edited parts (with pitch automation enabled) in real time to a new track.

EM contributing editor Michael Cooper is the owner of Michael Cooper Recording in Sisters, Oregon. Visit him atmyspace.com/michaelcooperrecording.

Step-by-step instructions on page 2

STEP-BY-STEP INSTRUCTIONS

Step 1:

Select the sound bite you want to edit, then choose the proper pitch mode from the Audio Pitch Correction submenu.

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Step 2:

Choose Pitch in the track's track-layer menu.

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Step 3:

Adjust the degree of pitch segmentation using either the Pitch Separation slider or DP's Mute and Scissor tools.

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Step 4:

Click-and-drag pitch segments up or down to transpose their associated notes in half-step increments. Command-drag to fine-tune, or use the Quantize Pitch command to center the pitch exactly.

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Step 5:

Toggle the Pitch Bypass button on and off during playback to compare your edits with the original melody.

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Step 6:

To render your changes, merge the edited sound bite or bounce it to another track (shown here), with pitch automation enabled.

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ONLINE LINKS

Mike Levine's review of Digital Performer 5.1 in the November 2006 issue of EM
emusician.com/sequencers/emusic_motudigital_performer_mac_2/

Digital Performer on the MOTU Web site
www.motu.com/products/software/dp