So, like, as far as i know, tracker music is made up of samples, like, i think of it as "lego pieces"
you mix and match those "legos" into music.
But where to get samples from?
You can go to Help -> Web Resources in OpenMPT, there's a small list of sample sites, or visit the Sample Sites (https://forum.openmpt.org/index.php?topic=174.0) topic right here on the forum. Since that topic has been going on for more than 15 years, many older links will probably not work anymore so it's best to browse it back-to-front.
Just in case downloading samples from the internet might not float your boat,
you can also ask about sample kits at some music store that sells computer music products,
so maybe there you can get a sample pack on a cartridge that can plug into the computer.