The Alternative Csound Reference Manual
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# expon

expon -- Trace an exponential curve between specified points.

## Description

Trace an exponential curve between specified points.

## Syntax

ar expon ia, idur1, ib

kr expon ia, idur1, ib

## Initialization

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

ib, ic, etc. -- value after dur1 seconds, etc. For exponentials, must be non-zero and must agree in sign with ia.

idur1 -- duration in seconds of first 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 or more specified points. The sum of dur values 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 last-defined segment to continue on in the same direction.

## Examples

Here is an example of the expon opcode. It uses the files expon.orc and expon.sco.

Example 1. Example of the expon opcode.

    /* expon.orc */
    ; 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
    /* expon.orc */

    /* expon.sco */
    ; Table #1, a sine wave.
    f 1 0 16384 10 1

    ; Play Instrument #1 for two seconds.
    i 1 0 2
    e
    /* expon.sco */

## See Also

expseg, expsegr, line, linseg, linsegr

## Credits

Example written by Kevin Conder.

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