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The Synthesis Process Introduction Representing Sound Waveforms Synthesis Modules Musical Expression 28. Change Over Time 29. Time Variant Controllers 30. Envelope Generators 31. Low-frequency Oscillators Control of Synthesis MIDI Part I MIDI Part II MIDI Part III Further Information Glossary Site Map About

28. Change Over Time

Changes in timbre, pitch and dynamics are central to creating music of any kind. Because music unfolds in time, a single composition will contain millions or perhaps billions of changes, from note-to-note variations to the nuances of tonal color and pitch that great artists make with even a single note in a performance.

Good musicians are keenly aware of the expressive power of inflections in tone, pitch and dynamics. The sudden accent, the gentle vibrato, the piquant tremolo are just a few of the expressive tools available. It is the gifted use of such expressive choices that marks a virtuoso as a genius.

Indeed, the listener actually associates the expressiveness of a performance with, and judges its quality by, these subtle, and sometimes not so subtle, changes in the music. Therefore, if a synthesis system is to be used expressively, it must have a means for creating changes, both suddenly and gradually, in all aspects of the sound being produced.

Listen to the following three musical examples and take note of the change in the qualities that convey a sense of expressiveness.

Example 28-1: Examples which demonstrate the musical expression of change over time.

In a synthesis system, these changes are induced by time-variant controllers. A time-variant controller will cause change in some aspect of sound over time.