Third Relation

The other night I was screwing around on the piano playing various cords instead of doing 'real' practice (as is my custom lately) and found something very interesting (to me anyway). I found that a B flat major triad in 1st inversion (D,F, and Bb) followed by D major triad in root position (D,F#, and A) sound really cool together. I was trying to figure out what cord progression this is (V to IV for example) when I realized that Bb is not even in the scale of D major. This sorta blew my little pee brain since I was operating under the notion that all things harmonic can be described by cord progressions using roman numerals. Then I noticed that D is the third degree of Bb major.

I asked a friend and she said that this is called a 'Third Relation'. I've looked on the Internet and in several theory books, but cannot find anything that describes a 'Third Relation'.

Anybody care to explain this very simply?

Hi Jory:

From just two major triads It's hard to develop any type of chord progression. Bb/D to D certainly doesn't resolve. Have you tried adding a third chord like this:

Bb/D-D-G/B

This is the equvalent of

bIII-V-I

in G-major. The Bb chord is borrowed from the parallel key of G-minor. Remember: a III chord in G-minor is a major triad (Bb) and G-minor has two flats. If you play the D chord as the V of G, it resolves to G. It sounds even better if you play D7 instead of just D like this:

Bb/D-D7-G

Try it! Hope this helps.

Hey Jory, I'm not surprised that you found that progression 'cool' sounding. That cool sound is taken advantage of very often in movie scores, particularly 'space' related movies. Also, Sibelius stumbled across it at times and in the beginning of the development of the first movement of his fisrt symphony he blurts it out quite literally. Also, listen for it in the first movement of Mahler's third (in the woodwinds) you can't miss it.

Happy listening,

Jeff