SQ Tracker and Sample Tracker was my main tools in the days of ZX Spectrum (for those who don't know, it was created by people from Czech republic, SQ is shortcut of Scalex and Qjeta (very very good musicians)). I think it was MQM2 demo from MQM team where was for first time showcased capabilities of Sample tracker.
I purchased version 3D, which was for D40 disk drive from Didaktik Skalica (5,25 DD), this disk drive features also parallel 8255 port, which can be used for many tasks, but for us musicians it is more important that you can implement 8-bit D/A converter into that port and experience quality of sample playback almost as on Amiga, instead of 4-bit playback on AY chip. Only thing that was bad, was crashes on 48k Spectrum (clone Didaktik M from Didaktik Skalica which "features" very bad russian ULA etc. (megademos like Shock was performed for example very badly)) with AY interface Melodik and D40 and D/A converter so i later purchased spanish ZX Spectrum 128k+ with Datel +D disk interface with 3,5" drive and some additional hw, which was zillion times more stable.
