Instruments / .sf2 files

hi, when adding .sf2 to the View > Instruments... dialog you're only telling that there will be some human readable names (for MIDI banks and programs, instead of magical numbers) that some instrument, plugin, internal soft or external hardware (outboard) are going to understand when switching presets, yeah, that's only going to happen via MIDI bank_select (CC#0, CC#32) and/or program_change (PC#) messages. you now know what :)

it doesn't bring any sounding instrument into play whatsoever (how could?)--it's just a convenience for you, to select and switch presets by name on-the-fly, on a MIDI Track Properties dialog or main menu Track > Instrument > etc. in the good old way of Cakewalk Pro Audio series, the predecessor of Sonar while in the late century era;)...

and no, qtractor won't ever have any built-in instrument player, of any kind nor genre--it is a sequencer, for x sake: you may use whatever instruments you like best... however the problems you report about different machines are most probably a concern of different and misaligned system and/or plugin shared libraries; notoriously, this is the case for the Calf-suite (and some old others...)

in this brave (GNU/Linux) world you just have to pay attention and care that all components are (or have been built/compiled) to the very same standards; yeah I kown it's a curse and a PITA; it has been for quite a while and it won't get solved soon anyhow. sorry.

hth.
cheers