Phasal Music

There's this game my roommate and I like to play with each other. She's a big indie rock fan, and I love metal and industrial punk. Whenever she plays indie, I have to start blasting metal from my speakers. And whenever I'm at my computer headbanging, she has to start playing a sugary-sweet indie tune from her speakers. We call it the indie-metal battle.

The coolest part of this game, though, is when we both have the same song- then we both start playing it at the same time. It usually ends up slightly out of phase with itself. When that happens, it's the coolest part of the song. It sounds like an echo.

When you play a song slightly out of phase with itself, from two different speakers, it starts to sound different depending on where you stand in the room. It's a very cool effect, and if you have two speakers in the room, it's an easy thing to try.

A famous example of this is the experimental song Come Out by Steve Reich. This song focuses on the phrase "come out to show them" (there's a huge backstory,) which starts off as one track, but is really 16 or so different tracks playing out of phase with each other. By the middle of the song, the original phrase is completely unintelligible and it just becomes a rhythmic phrase that changes extremely slowly. Unless you listen closely, you can barely hear the phrase changing.

It's a really cool song. If you play it from two different speakers, it starts to sound different depending on where you stand in the room. You don't even have to play it out of phase with itself.

But if you do.... Hmmm.

Any ideas, experience, or comments on playing phasal music?