rand — Generates a controlled random number series.


Output is a controlled random number series between -amp and +amp


ares rand xamp [, iseed] [, isel] [, ioffset]
kres rand xamp [, iseed] [, isel] [, ioffset]


iseed (optional, default=0.5) -- a seed value for the recursive pseudo-random formula. A value between 0 and 1 will produce an initial output of kamp * iseed. A value greater than 1 will be seeded from the system clock. A negative value will cause seed re-initialization to be skipped. The default seed value is .5.

isel (optional, default=0) -- if zero, a 16-bit number is generated. If non-zero, a 31-bit random number is generated. Default is 0.

ioffset (optional, default=0) -- a base value added to the random result. New in Csound version 4.03.


kamp, xamp -- range over which random numbers are distributed.

kcps, xcps -- the frequency which new random numbers are generated.

The internal pseudo-random formula produces values which are uniformly distributed over the range kamp to -kamp. rand will thus generate uniform white noise with an R.M.S value of kamp / root 2.

The remaining units produce band-limited noise: the kcps and xcps parameters permit the user to specify that new random numbers are to be generated at a rate less than the sampling or control frequencies.


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

Example 383. Example of the rand opcode.

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

; 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 rand.wav -W ;;; for file output any platform

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

; Instrument #1.
instr 1
  ; Choose a random frequency between 4,100 and 44,100.
  kfreq rand 20000
  kcps = kfreq + 24100

  a1 oscil 30000, kcps, 1
  out a1


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

; Play Instrument #1 for one second.
i 1 0 1


See Also

randh, randi


Example written by Kevin Conder.

Thanks to a note from John ffitch, I changed the names of the parameters.