Some time ago, tedd posed a question to the list concerning 
generation of variable frequency sounds. At first it appeared that 
current Macs are limited by their controller chips to generating only 
MIDI sounds. However, I discovered several apps that were able to 
produce variable frequencies down to fractions of a hertz independent 
of octave structure. I shared these with tedd, but to date am still 
stymied as to how the developers did this.

While studying Carbon, I came across a recommendation that a new command--
rateMultiplierCmd -- when used as part of the sound record, could be 
used to produce variable frequencies.

Here is the C code from Apple's developer web site:

OSErr RaisePitchOneOctave(SndChannelPtr chan)
{
SndCommand cmd;
OSErr err;

cmd.cmd = rateMultiplierCmd;
cmd.param1 = 0;
cmd.param2 = 0x00020000; // rate of 2.0

err = SndDoImmediate(chan, &cmd);
return (err);
}

Here is my FB^3 translation of the C code (which may or may not be 
correct, but should serve as a basis for discussion. The C code above 
lists only one value form cmd.param2, but below I have commented out 
several others shown in a chart on Apple's sample code page.):

LOCAL
DIM err AS HANDLE
DIM @cmd
DIM @rateMultiplierCmd
LOCAL FN RaisePitchOneOctave( soundChannelPtr )

cmd.cmd = rateMultiplierCmd
cmd.param1 = 0

// Decimal value 1.0
// Plays sound at normal pitch setting (default)
'cmd.param2 = 0x00010000

// Decimal value 2.0
// Plays sound at a pitch shifted up one octave
cmd.param2 = 0x00030000

// Decimal value 0.5
// Plays sounds at a pitch shifted down one octave
'cmd.param2 = 0x00005000

// Decimal value 1.5
// Plays sounds at a pitch shifted up half an octave
'cmd.param2 = 0x00015000

// Decimal value 0.0
// Repeat last audio sample indefinitely,
// which effectively pauses playback on this channel
'cmd.param2 = 0x00000000

err = FN SNDDOIMMEDIATE( soundChannelPtr, cmd )

END FN

My question to the list is, can anyone see how to incorporate this 
code into a working demo? It appears that by altering the second cmd 
parameter, this function could be used to generate a variety of 
frequencies (probably more accurately described as pitch shifts). But 
as to implementation, I'm stuck.

Ken