ENVELOPING: Detailed Information

by Archer Endrich

Key Features of the CDP ENVELOPING Functions

• Amplitude envelope extraction can be done all at once, or extracting and imposing the envelope can be done in separate operations. The advantage of the latter is that an envelope file is created which can then be applied to different sounds.



• FORMANTS VOCODE operates in the spectral domain and concerns the spectral envelope, the ever-changing pattern of frequency content in the sound.



• It is also possible to work with the resonant frequencies of a sound, i.e., its formants. FORMANTS GET and FORMANTS PUT similarly extract and impose this kind of data between sounds.



• Envelopes can be shaped by hand, as it were, by creating envelope breakpoint files, either with a text editor or with one of the graphic breakpoint editors available in the CDP software.



• There are many other ways to shape envelopes with CDP software, such as emphasising the attack, creating a plucked effect, dovetailing the start and end of a sound, normalising, time-reverse, exaggeration, attenuation, raising, time-stretching, flattening or gating the envelope.

Some possible musical results with ENVEL

• Ebb and flow of a sound by splicing (or mixing with overlap) forwards and reversed versions of a fairly steady-state sound, then a DOVETAIL with linear shape to/from the centre point of the whole sound: thus it gradually rises from and returns to silence.



• Reshaping the existing amplitude contour with a specially designed breakpoint file (ENVEL REPLACE, Mode 3), or with one of the 15 different processes available in ENVEL REPLOT (input is a breakpoint file), ENVEL RESHAPE (input is a binary envelope file), or ENVEL WARP (input is a soundfile): Normalise, Time reverse, Exaggerate, Attenuate, Lift, Time-stretch, Flatten, Gate, Invert, Limit, Corrugate, Expand, Trigger bursts, Move to ceiling or Duck.



• Introduce amplitude tremolo (ENVEL TREMOLO).



• Emphasise the beginning of the sound (ENVEL ATTACK and ENVEL PLUCK).



• Transfer the amplitude or spectral envelope from another sound, as illustrated by these examples.

Other forms of enveloping in CDP

• All breakpoint files create time-varying contours which in effect envelope that particular parameter, such as upper and lower pitch contours in a texture.



• Pitch shapes can be extracted from several sounds and then combined in different ways as transposition files, thus imposing shapes from one sound onto another.



• Any text breakpoint file can be converted to an amplitude envelope file with ENVEL BRKTOENV. Thus, for example, you could extract a pitch contour, saving as a breakpoint file, convert it to a binary envelope file and impose it on a different sound.



• DISTORT ENVEL and DISTORT REFORM modify the existing wavecycle envelope shape with some other envelope shape.



• STRANGE WAVE oscillates between harmonic and inharmonic states, which results in a kind of vibrato.



• ENVEL TREMOLO produces an amplitude tremolo.

General observations

• Enveloping is one of the most common and important shaping processes in sound design.



• Envelope shapes are easily perceptible and form musical gestures which grab the attention and define the character of the music.



• Envelope shapes are also used to build relationships between sounds, which serves to create an organic wholeness to the music. This can be done with amplitude envelopes, spectral envelopes (i.e., formant shapes: cross-synthesis) or across different parameters.

Last updated: 4 December 2003