s = Server.local;
s.boot;
s.quit;

(
SynthDef("test", { arg freq=220;
var sound;
sound = SinOsc.ar(freq);
Out.ar(0, [sound, sound]);
}).writeDefFile;
s.sendSynthDef("test");
)

z = Synth("test");
z.set("freq", 555);
z.free;