expon
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## expon

expon — Trace an exponential curve between specified points.

## Description

Trace an exponential curve between specified points.

## Syntax

    ares expon ia, idur, ib

    kres expon ia, idur, ib

## Initialization

ia -- starting value. Zero is illegal for exponentials.

ib -- value after idur seconds. For exponentials, must be non-zero and must agree in sign with ia.

idur -- duration in seconds of the segment. A zero or negative value will cause all initialization to be skipped.

## Performance

These units generate control or audio signals whose values can pass through 2 specified points. The idur value may or may not equal the instrument's performance time: a shorter performance will truncate the specified pattern, while a longer one will cause the defined segment to continue on in the same direction.

## Examples

Here is an example of the expon opcode. It uses the file expon.csd.

Example 142. Example of the expon opcode.

See the sections Real-time Audio and Command Line Flags for more information on using command line flags.

    <CsoundSynthesizer>
    <CsOptions>
    ; Select audio/midi flags here according to platform
    ; Audio out   Audio in
    -odac           -iadc    ;;;RT audio I/O
    ; For Non-realtime ouput leave only the line below:
    ; -o expon.wav -W ;;; for file output any platform
    </CsOptions>
    <CsInstruments>

    ; Initialize the global variables.
    sr = 44100
    kr = 4410
    ksmps = 10
    nchnls = 1

    ; Instrument #1.
    instr 1
      ; Define kcps as a frequency value that exponentially declines
      ; from 880 to 220. It declines over the period set by p3.
      kcps expon 880, p3, 220

      a1 oscil 20000, kcps, 1
      out a1
    endin

    </CsInstruments>
    <CsScore>

    ; Table #1, a sine wave.
    f 1 0 16384 10 1

    ; Play Instrument #1 for two seconds.
    i 1 0 2
    e

    </CsScore>
    </CsoundSynthesizer>

## See Also

expseg, expsegr, line, linseg, linsegr

## Credits

Example written by Kevin Conder.

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