More about instruments

[Risike]

I've read a lot of code about music management on the Gamebuino. I think all is ok for me except a little thing.
I don't understand how to create a new instrument.

When i look the Gamebuino Sound.cpp file I can see this :
const uint16_t squareWaveInstrument[] PROGMEM = {0x0101, 0x03F7};
const uint16_t noiseInstrument[] PROGMEM = {0x0101, 0x03FF};

But what are these numbers (0x0101, 0x03F7 and 0x03FF) ?

Thanks