randh — Generates random numbers and holds them for a period of time.


Generates random numbers and holds them for a period of time.


ares randh xamp, xcps [, iseed] [, isize] [, ioffset]
kres randh kamp, kcps [, iseed] [, isize] [, ioffset]


iseed (optional, default=0.5) -- seed value for the recursive pseudo-random formula. A value between 0 and +1 will produce an initial output of kamp * iseed. A negative value will cause seed re-initialization to be skipped. A value greater than 1 will seed from system time, this is the best option to generate a different random sequence for each run.

isize (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. randh will hold each new number for the period of the specified cycle.


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

Example 384. Example of the randh 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 randh.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 200 and 1000.
  ; Generate new random numbers at 4 Hz.
  ; kamp = 400
  ; kcps = 4
  ; iseed = 0.5
  ; isize = 0
  ; ioffset = 600

  kcps randh 400, 4, 0.5, 0, 600
  printk2 kcps

  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 5


See Also

rand, randi


Example written by Kevin Conder.