Tetrachordal Trickery


I'm always looking for ways in which scales can be used without sounding so much like... well... scales. The following flight of fancy has its roots in a recent discussion on the Usenet group rec.music.makers.guitar.jazz.

There's a lot of stuff on my site already about thinking "chord-on-chord" and using interval patterns from scales, etc. This idea comes from thinking about a familiar scale in what might be a not-so-familiar way...

A tetrachord is a four-note series of pitches, usually arranged within the space of a perfect fourth. For example, the series C D E F is called a major tetrachord. The series C D Eb F is usually called a minor tetrachord. (The term "tetrachord" comes from Greek musical theory; the Greeks recognized three types of tetrachords in which the outer notes were a perfect fourth and the middle two voices varied. But their tuning system was something we can only approximate; it's highly unlikely that their music sounded much like ours, anyway. Their tetrachord types were diatonic, enharmonic and chromatic, FYI.)

By combining tetrachords, we can produce scales.

Take a major tetrachord on C (C D E F) and a major tetrachord on G (G A B C); stick 'em end to end and you get a C major scale (C D E F G A B C).

Take a minor tetrachord on C (C D Eb F) and the same G major tetrachord, and you get C melodic minor (C D Eb F G A B C).

Okay, let's get kinky. Combine a C minor tetrachord and an F# minor tetrachord; you get C D Eb F F# G# A B. Stare at that for a second or two and you realize it's a C whole/half diminished scale. Cool. So if I choose to, when I'm playing in a harmonic situation in which that scale could be used, I could concentrate on either one of those tetrachords at a time instead of thinking about the whole diminished scale. Or I could make up lines that flow from one tetrachord to the other. Very interesting. Wonder how that would sound? Well, think about it and I'll see you next time.

'Bye now.

Just kidding. You didn't really think I'd leave you without an example, did you? Click here (Acrobat Reader needed) to see a sample line using tetrachords from the C diminished scale. Click here (mp3 player needed) to hear me playing the line.

Hope you enjoyed this little diversion. As with all of the theory stuff on this site, use it to help you discover some new sounds to play with. Then learn to hear the sounds so you don't have to think about all this while you're playing!