Apple Logic Express 7 - Manual (Page 79)

Chapter 12 Synthesizer Basics 79
Other Oscillator Waveforms
Waveforms (waves) are named sawtooth, square, pulse, or triangular because of their
shape when displayed as an oscillogram (as in Logic’s Sample Editor). This is the
triangular wave:
The triangular wave has few harmonics—which is evident by the fact that is shaped
more like a sine than a sawtooth wave. This wave contains only odd harmonics—which
means no octaves.
Envelopes
What does the term envelope mean in this context? In the image, you see an
oscillogram of a percussive tone. It’s easy to see how the level rises immediately the
top of its range, and how it decays. If you drew a line surrounding the upper half of the
oscillogram, you could call it the envelope of the sound—a graphic displaying the level
as a function of time. It’s the job of the envelope generator to set the shape of the
envelope.
The screenshot shows a recording of an ES1 sound created with these ADSR (attack
time, decay time, sustain level, and release time) parameter settings: attack as short as
possible, medium value for decay, zero for sustain, medium value for release.