ChucK/fm.ck

 // carrier
 sinosc c => dac;
 // modulator
 sinosc m => blackhole;

 // carrier frequency
 220 => float cf;
 // modulator frequency
 550 => float mf => m.freq;
 // index of modulation
 .5 => float index;

 // time-loop
 while( true )
 {
     // modulate
     cf + (index * mf * m.last()) => c.freq;
     // advance time by 1 samp
     1::samp => now;
 }