In milkytracker FT2 clone it is possible to draw your own samples to create basic instruments, most of the stuff for instruments is indeed samples often ripped from other modules as is a common practice to get a library of sounds going.

Additionally old competitions used to provide packs of samples and 1 hour to make a composition on which it was then voted, another nice way to spend an evening and get some free instruments :)

A lot of trackers work with synthesized sound, even some early trackers were synth-only. Modern ones have improved on this, eg. Sunvox, Buzz and others are mostly defined by their synths and effects, and how well those things integrate with the tracker interface.