SOUND

CLEAR LOCAL
  DIM myRate&
  DIM mySndCmd.sndCSize
  DIM myErr
LOCAL FN MyHalveFreq (mySndChan&)
'Get the rate of the sample currently playing.
  mySndCmd.cmd% = _getRateCmd ' the command is getRateCmd}
  mySndCmd.param1% = 0 ' unused}
  mySndCmd.param2& = @myRate&
  myErr = FN SndDoImmediate(mySndChan&, mySndCmd)
  LONG IF myErr = noErr
' Halve the sample rate
    mySndCmd.cmd% = _rateCmd ' the command is rateCmd
    mySndCmd.param1% = 0 ' unused
    mySndCmd.param2& = FN FixDiv(myRate&, &H00020000)
    myErr = FN SndDoImmediate(mySndChan&, mySndCmd)
  END IF
END FN = myErr


untested, but should work.