Electronic Studio Resources I: Assignment 3 — Short Piece

Assignment 3: Short Piece

What we’re trying to do

Make a short composition using audio in Digital Performer. It should:

last about two minutes,
build on skills you learned in the first two assignments,
include volume and panning changes,
include time-scaling and pitch-shifting,
include EQ (equalization), reverberation, delay, and other real-time plug-in effects.

What to turn in

One Digital Performer project folder, with the assignment number and your login as part of the folder name. Drag the folder into the DropBox folder for Assignment 3 on the computer in the studio.
One AIFF (or WAVE) file containing the final mix (created with the Bounce to Disk command). Name the file with your piece title and your own name. Drag this into the DropBox as well.
Write an email to me (Prof. Gibson), giving me the title of your piece and a few sentences about how you made it, what it’s about, and so forth. Tell me what you like best about it, and what I should listen for.

After you turn it in

We will play your compositions in tutorial.
These projects will receive letter grades.
Grades will be based on overall conception and execution, the quality of the source recordings, your sonic imagination, attention to detail, sensitivity to spatial (panning, reverberation) and spectral (EQ) qualities, following the instructions (including submission requirements), and completion of the project email.

The basic idea

You are to create a piece using only sounds you record yourself. (You may use any of the sounds you recorded for Assignment 1, plus any more that you’d like to record.)

Please DO NOT use any of the following for this assignment:

sounds from the Kurzweil (or other) keyboards,
sounds copied from sound effect CDs or audio CDs,
sounds copied from Internet sites,
finished passages of music played on instruments (isolated sounds are okay), or
passages from recordings of your own acoustic pieces.

This may seem restricting, but you can do a lot with just a small collection of sounds, if you take advantage of the time-scaling, pitch-shifting, filtering, and other effects in Digital Performer.

One possibility to consider is the imposition of pitch onto sounds, even those that seem not to have any pitch. One way to do this is with tight band-pass EQs, such as in the Periscope plug-in. Another way is to use a resonating delay line (a delay with high feedback and delay times less than 50 milliseconds). If a sound already has pitch — and is monophonic, and cleanly recorded — you can use the DP pitch automation to change its pitch.

Below are descriptions of techniques you should perform while in the process of building your project.

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 (Project menu).
Move the mouse over either edge of the soundbite — over the top of the soundbite rectangle. 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 (in the Audio Files folder) 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 the soundbite, and choose Region > Transpose.
Make sure the Transpose Audio check box is ticked.
Just below that, choose Transpose audio by creating new soundbites.
Specify an interval of transposition, using the from and to fields. (Highlight a field, and play a note on a MIDI keyboard to set a pitch.)
Press the Apply button.

Note that this type of transposition preserves formant frequencies.

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.

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 handle formants in any special way, 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 buried in the Sound File Information window (Studio > Sound File Information).

Volume and Pan Automation

You can change the volume and panning of a soundbite while it plays. You do this either with the Mixing Board, or by manipulating “rubber band” lines in the Sequence Editor.

Here’s how to do it in the Mixing Board.

Open the Mixing Board (Project menu).
Press the automation record-enable buttons for the tracks whose volume or pans you wish to vary. (These buttons turn red.)
Play the sequence. (That’s right: play, not record.)
Wiggle the knobs and slide the faders, as you desire.
Stop playing the sequence, and turn off the automation record-enable buttons, so as to prevent accidental changes.
Now when you play the sequence, the faders and pan knobs will move, as long as the automation play-enable buttons are depressed. (These buttons turn green.)

Here’s how to change volume using the “rubber band” lines.

Open the Sequence Editor. At the left of each track is a control panel. A pop-up menu lets you select different editing modes. Normally you’ll see Soundbites here. This mode lets you drag your soundbites around and edit them.
Choose Volume from this pop-up menu. Now any soundbites in the track are dimmed, and you can use the pencil tool to draw a volume line. (If you don’t see the Tool palette, choose Tools from the Studio menu.) The volume line works by “connecting the dots.” You supply the dots, and the program draws lines between them to ramp the volume from one state to another. Digital Performer calls one of these dots an audio volume event, which you can edit very precisely in numeric form.
The volume lines you’ve drawn may display as dotted lines. This means that automation is not play-enabled for that track. If you play the track, you won’t hear any volume changes. You can play-enable automation using the Mixing Board (as described above), or you can use the handy Auto pop-up menu in the Sequence Editor control panel.
You can drag the dots around to change the shape of the volume line. Click on a dot and press the delete key to delete it.

The audio volume event values are expressed in decibels (dB). A value of 0 dB means the audio plays from the disk with no amplitude scaling. If you shape the line so that it goes above 0 dB, the audio samples will be multiplied by a factor greater than one, and you could easily cause clipping (digital distortion). If this happens, the track’s meter in the Mixing Board will show it.

Panning works similarly to volume:

Choose Pan from the same editing mode pop-up menu from which you chose Volume.
Shape the line just as you did for the volume line. To pan to the left channel, drag a dot to the top of the graph. To pan to the right channel, drag to the bottom. The vertical center of the graph corresponds to the center of the stereo field.

Choose Soundbites from the editing mode pop-up in order to edit soundbites again.

Shortcut: Hold the option key down while selecting an editing mode (e.g., Soundbites, Volume, Pan) from any audio track’s popup menu: all tracks will change to that mode.

Audio Effects

One of the great things about using audio in Digital Performer is that you can use audio effects.

To use an effect on a track...

Open the Mixing Board.
Choose an effect from one of the insert pop-up menus at the top of the Mixing Board for one of the tracks. This is a little confusing, because
- you might not be able to see the top of the Mixing Board (scroll the view up to see the top), and
- these pop-up menus start out blank, as in the graphic below.
  
  Just press and hold the mouse button on one of the arrows, and you’ll see an effects menu. Choose an effect.

There are five vertically arranged effect slots for each track. The audio flows from the top insert to the one below, and so on, down through all five. So if you have a Chorus effect in the top insert, and an Echo effect in the one below that, the dry sound from the track will be chorused first, and then echoed. Switching the order of effects often gives you a different result.

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.

You can move an effect from one insert to another in the same track, or in a different track, by holding down the command (Apple) key while dragging the effect name in the Mixing Board. Hold down the command and option keys while dragging to copy effect settings. Click the effect name while holding down the option key to bypass (temporarily disable) the effect.

The best way to get started with effects is to try the presets that most of them include. Select these from a pop-up menu, as 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.

Graphic Equalizer: Periscope

Periscope is a Digital Performer plug-in that performs a real-time spectral analysis on the audio in a track and lets you change the amplitudes of the frequency bands.

In the Mixing Board, choose AudioEase > Periscope as an insert effect for a track.

The top portion of the Periscope window gives you 32 frequency bands of EQ, with sliders to control the amount of boost or cut for each band. The bottom portion of the Periscope window lets you adjust the frequency range within which the 32 sliders operate. Drag the red and yellow needles around to set a range. Notice that the calibration of the sliders changes to show just frequencies within that range. Sliders on the left and right ends are low and high shelf EQs, respectively. Sliders in between are peak/notch EQs.

The fader edit mode buttons at the bottom right of the plug-in window control how your mouse movements affect the positions of the sliders. Free draw lets you draw a curve without any constraint. Magnetic lets you drag one slider while its neighbors move to form a smooth curve. The magnetism knob controls the smoothness of the curve.

You also see, underneath the sliders, a real-time graph of the sound, post-EQ. (Actually, there are two graphs: the green graph shows peak amplitude, while the blue graph shows average amplitude.) This helps you evaluate the strength of frequency bands.

Play around to see how dramatically you can change the sound. Unlike the Parametric EQ plug-ins, Periscope lets you make very steep, “brick wall,” EQ shapes.

Using a Master Fader Track

When mixing, you should make sure that none of the tracks clips — that is, that none of the track meters in the Mixing Board light up the red clipping indicators.

But even if you have no clipping at channels, it’s still possible for the combination of all your channels — the addition of these signals into a stereo mix bus — to result in clipping. The only way to see this, and to do something about it, is to use a master fader track.

Create a master fader track by choosing Project > Add Track > Master Fader Track. This track holds no soundbites. It merely gives you a single volume fader that controls all of your audio tracks together. Adjust this fader while playing your sequence so that the meter for the Master Fader track, shown in the Mixing Board, never turns red.

Bouncing to Disk

Here’s how to get your audio into a form from which you can make audio CDs or MP3s.

Make certain all audio track outputs are set to Analog 1-2.
Select all the audio tracks you want to include in your mix file. Shift-click the track names in the Tracks view to select them. You don’t have to include the Master Fader track in the selection. Your audio tracks — and the Master Fader track — must be play-enabled.
Use the Selection Information view (Studio menu) to fine-tune 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.
Choose Audio > Bounce to Disk. Use the following settings in the dialog that appears.
- File Format: AIFF, Interleaved
- Channels: Stereo
- Resolution: 16 Bit Integer
- Import: Do not Import
- Source: Analog 1-2
Press the Choose Folder button, and navigate to the Desktop.
Press OK. Another window will pop up, but you can just OK it. Your mix file will appear on the Desktop. This is the file you should copy into the CECM server Shared folder.

Some Sound Modification Tools

Here are some programs that let you change sound in ways not easily achieved inside Digital Performer. Right-click on one, choose Download Linked File As, and save it on the Desktop. Then double-click the .zip file to uncompress it. Open the folder to find the program. You don't have to install this anywhere.

These programs let you import an audio file, process it, and then record the results into another file. Then you can add that to your DP project.

Before working with these, you'll need to click the Audio Driver button at the top-left corner of the window, and choose CoreAudio MOTU 828mk2 from the Driver pop-up menu. Then close the DSP Status window.

To use, first click the speaker icon. Drag a sound file onto the Play button, check the Loop box, and press Play. Fiddle with the controls. If you like the sound, press Record to start real-time recording of the output to a sound file. Press the right-hand Stop button to stop recording.

ResonatorBank
FilterBank
MultibandDelay
Granulator