5. Arguments & Controlling Synths

Arguments in Functions

Arguments allow one to pass information to a function when the function is evaluated. For example:

f = { arg a, b;
    a - b;
};

In the above function we declare two arguments, a and b. This enables us to pass in two values every time we evaluate the function like so:

f.value(3,2);

Which returns 1. We could run this repeatedly with different values and expect similar results: the first argument will be subtracted by the second one.

There is a syntax shortcut for writing arguments which we can use to rewrite our function above to:

f = { | a, b|
    a - b;
};

So one can declare arguments for a function in one of two manners:

1. arg nameofargument1, nameofargument2;
2. | nameofargument1, nameofargument2|

While this may sound esoteric, it's important to understand that many aspects of Supercollider, like arguments, allow a programmer multiple stylistic options in terms of how he or she writes their code.

Arguments in UGens

There are three strategic opportunities provided by deliberate use of arguments in SC:

1. arguments provide helpful labels to different parts of a UGen (a kind of memory aid)
2. arguments set default values for a UGen (example: every time I run this Synth the volume starts at half its total signal strength [0.5])
3. arguments reserve a way to change a particular part of a UGen once it is running (example: I start my Sine tone playing a frequency of 440Hz but will change it to 200Hz later)

In general I think of arguments as things I need to control or change in UGens when I am using them.

Relevant Argument Names

In order to come up with relevant argument names one often references the Documentation. Go to the help file for SinOsc as an example (note: to access the help you select the reserved word and hit Command + D) and scroll down to the section labeled Class Methods. It should look like this:

The first argument in SinOsc is frequency, the second phase, and the third mul (short for multiply).

Using this information one can rewrite this:

{ SinOsc.ar(440, 0.0, 0.5) }.play;

to this:

{ | freq = 440, phase = 0.0, amp = 0.5| SinOsc.ar( freq, phase, amp) }.play;

Note: I prefer to use amp instead of something like mul or multiply.

Controlling Synths

If we store the SinOsc from above in a variable like x:

x = { | freq = 440, phase = 0.0, amp = 0.5| SinOsc.ar( freq, phase, amp) }.play;

we can control it using the .set method of Synth:

x.set(\freq, 200);

One can .set any argument declared as part of the function once the Synth is running, and can even make changes to multiple arguments simultaneously like so:

x.set(\freq, 300, \amp, 0.2 );

To clear the Synth from the server one can simply .free it:

x.free;