[vwelling]

Most tracks can be split up into four distinct components: drums, bass, melody, and vocals. Of course, they could have taken it a step further, by splitting a track up into its individual instruments, but I doubt that would be very usable in a live performance setting (although some performers actually do go this route, usually relying on software such as Ableton Live for this purpose).

The four channels are also quite similar to the EQ section of a DJ mixer which generally controls three frequency ranges (low, mid and high). EQ-ing is heavily used to mix songs together, so by sticking to a similar interface, DJ's can easily pick up this format.

[soylentcola]

I'm more of a "for fun" DJ (occasional parties, events, but mostly just my basement) but I'm tempted to try mapping the 4 stem tracks to the 4 knobs on my basic controller (gain, high, mid, low) in Traktor since it apparently supports the format. Probably not something I'd want to have permanently enabled but an easy way to play around with it. I guess if I wanted to map a key to toggle between EQ and stem track levels it might work.