;) i guess 'non-technical' description of MBSID birth is unavoidable. Thorsten, first of all thank you for answer. True, i could't find any bits of information about it, nowhere. You're the only source, which must be documented. ::) Lot of folks not realizing it, that's ok with me. Why you chose SID chip as a heart? Why not other sound-generating capable chips, which were widely available back then as well? Is this was simple love of SID sound which you got experienced while working/playing with commodore software? ;) /edit: ...or accidental availability of that c64 at your closet to take out and experiment? Or maybe both...