[chromoblob]

Meanwhile, there's GoatTracker (tracker for SID music).

[daneel_w]

And SID Factory and a couple of others.

[mdp2021]

Any recommendation for Multi-SID? There should exist a six channels GoatTracker - I am not sure anything else is available.

[terlisimo]

cheesecutter apparently also supports dual sids: http://chordian.net/c64editors.htm