Still more variations can be achieved by changing the relative output levels between operators; the greater the level of the modulating operator, the more harmonics are present.

FEEDBACK

Note that every algorithm’ has one operator with a “feedback loop”-represented by a line from the output of the operator which feeds back to the input of the same operator. In effect, a feedback loop means that the operator is modulating itself. While every algorithm has one feedback loop, feedback is not necessarily used in every voice. One of the DX27 editing functions permits the feedback level to be set between 0 (no feedback) and 7 (maximum feedback).

ENVELOPE GENERATORS

Consider what happens when you play a note on an acoustic instrument. The level of the sound initially goes up to some value, then eventually falls to nothing, following a pattern that is characteristic of the particular instrument played. For ex- ample, a low note on a pipe organ starts slowly when you press a key, because it takes a while for the large column of air within the pipe to build up to maximum oscillation level, and takes a while to die down once the key is released. A note played on a wood block, on the other hand, starts quickly as the mallet strikes the block, and stops quickly as the block stops resonating. The characteristic volume pattern of any note played on any instrument is known as its “volume envelope.” Most acoustic instruments also have a “timbre envelope,” in which the harmonic

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