Add unison parameter

[fpesari]

Many (virtual) analog synths have a Unison option which allows playing multiple voices when a single note is played. These voices are detuned (with a knob) and allow creating particularly "phat" sounds, as heard in British bass music or in leads like Supersaws.

It'd be nice if amsynth had a Unison option 😄

[nickdowell]

It would be an awesome feature! 😎