JJOS instrument programs

I think I basically understand what a JJOS instrument program is, and I definitely understand the concept of multi samples.

But how is an instrument program technically different than a drum program? What makes the instrument program special? Couldn't you just get a drum program or use an older OS and make a program of multi samples and basically get the same result? Or is there something extra the instrument program contains?

Yes, as you said you can build in drum program also. Main difference is there is one filter/lfo/etc over whole INST program vs filter/lfo per pad in DRUM. Also in INST program one can have more "layers" over single note.

I think you have that backwards, layers can be done with DRUM programs up to three and INST programs are limited to just one.

Another advantage of INST programs is that the key range can be expanded to a full 88 keys as opposed to being limited to assigning notes to a pad which gives you 64 notes all together if you are using all pad banks.

I meant more sample assigment, forgot there is no velocity split on INST.