Feature request: ability to detune an instrument by n cents

[freq-mod]

Some instruments, like cymbals, hi-hats, triangles, etc would greatly benefit from it. The same can apply to OPL3-BE - when having dual 2-op voice, second voice can be detuned. If the voice 2 is pasted as voice 1, when creating a normal 2-op instr, detune information is lost.