Electronic Music Interactive, 2nd edition

Glossary

sample: each individual measurement of the instantaneous amplitudes of an analog representation of sound. These amplitude measurements are usually taken thousands of times per second.
sampling rate: the rate at which measurements of amplitude are taken; usually expressed in terms of number of samples taken per second. Sample rates of 44,100 per second and 48,000 per second are the most common.
sawtooth wave: a waveform that consists of all of the harmonics, whose relative amplitudes are expressed by the ratio 1/harmonic number, and whose even-number harmonics are 180 degrees out of phase.
sequence: a musical document that a MIDI sequencer records, edits and plays back that reflects a list of MIDI events.
serial: a type of transmission where bits of data are transmitted one at a time in a series. Serial transmission is used by the MIDI protocol.
sine wave: the single waveform with only one frequency.
slope: refers to how steeply, or acutely, a filter attenuates frequencies above (in the case of a low-pass filter) or below (in the case of a high-pass filter) the cut-off frequency.
sound: the perception of fluctuations of air pressure; we often divide sound into two parts that which is objective, quantifiable and adheres to physical laws, and that which is psycho-acoustic, i.e., subjective.
sound source: the object or thing that vibrates and causes the displacement of air molecules which we ultimately hear as sound.
square wave: a waveform that consists only of odd-numbered harmonics, whose relative amplitudes are expressed by the ratio 1/harmonic number, and whose harmonics are all in phase.
stage: refers to one of the segments of an envelope. Attack, decay, sustain, and release are the names of the stages of the common four-stage envelope.
status byte: one of two types of bytes in the MIDI protocol. Status bytes have numerical values ranging from 128 to 255 and commonly specify what is to be done, and often on what channel it is to be done. A status byte is always the first byte in a MIDI message and is identifiable because its first bit is always "1".
subaudio: refers to frequencies that are lower than humans can hear, approximately 20 Hz and below.
subtractive synthesis: a synthesis technique that is based on the removal or attenuation of specified frequencies by a filter.
sustain: the third stage of a four-stage envelope, but may have other meanings depending on context.
synthesis: refers to the designing of analog or digital representations of sound that ultimately are "output" by a synthesis instrument. There are a variety of synthesis techniques among which are additive synthesis (the combining of sine waves at multiple frequencies, amplitudes and phases), subtractive synthesis (the use of filtering techniques to remove specified frequencies of a complex frequency spectrum), or FM synthesis (the modulation of the frequency of one signal by the frequency of a second signal thereby generating frequencies).
synthesizer: an instrument that produces an analog or digital representations of sound, which the user may design. Presumably these "synthesized" sounds will be subsequently converted to acoustic energy so that we may hear them.