isn't there a PSG register bit you're not supposed to change? does the SOUND command have a safeguard for that (I hope)?
Register 14 and 15 are better left untouched. These two registers control the joystick ports.
The two most significant bits of register 7 should always be 10 (so reg 7 has a value of 10xx xxxx).
The two bits of reg 7 specify how the registers 14 and 15 are used.
SOUND 14,x or SOUND 15,x gives an illegal function call, but there's no safegueard against putting wrong values into register 7.
And apparently it is possible to damage hardware when writing values other than 10xx xxxx to register 7 
Yes , i read that part about the register mandatory settings.
but after reviewing the specs I think my biggest concern is adding modulation to the tuning...
every time the value changes, the adsr will be retriggered i think and that's not what i need...
i'll have to test it out....
Another thing, are there any binary files available with pre-calculated sinus-values
to create an LFO ? (low freq osc)
Creating a math routine is just ridiculous...what was i thinking ! 
