I've been thinking about how YouTube really is an amazing window on the world lately. Or rather, a window on an amazing world, full of people with talent that I would probably never ever get to discover, all competing for their 15 minutes of fame... I've learned one thing today, what multitrack ist. Basically people record different tracks of a song and then mix them together. Some of them do it also completely a capella (imitating the instruments). And I liked it. Especially those two:
and this one
Try a search on YouTube with "multitrack" as a keyword, there's much to stumble upon.