Music related post! Take heed....

[JWC]

Something is kind of bugging me. The difference between key changes and chord changes within a song. I think I know the difference but am highly unsure.

ok, if a song has the chords G,D, and C for example. is the whole song in G, or does the key change everytime chord changes. Does it change to the key of D or is it the D chord being played in the key of G???

[jazzbo]

It depends on the chords. C what? D what?

If a song has the chord changes:

Cmaj7 / Dmi7 G7 / Cmaj7 / Ami7 D7 / Gmaj7

then you have two chords (D7 and Gmaj7) that are not in C. The key starts in Cmaj, and Dmi7, G7, and Ami7 are all chords in Cmajor, but the D7 and Gmaj7 are not. It's a modulation. It changes keys, even if just for one bar, G major.

Look at the entire song, find what key it is in, and assign the value of chord within that key. So the above example starts in Cmajor, with the I chord, then ii-V changes resolving back to the I, but then you have the vi then a dominant ii, which is really the ii-V change resolving to G major.

[JWC]

yeah, well when you go from I to IV to V, are you changing keys??

[jazzbo]

No. If you're playing something in Db major (because we all know how often 12 bar blues come up in Db ), then you're I-IV-V changes are:

Dbmaj7 - Gbmaj7 - Ab7

All of those chords appear naturally in the scale. I guess, if you play the Gbmaj7 as G7 you're playing a chord that doesn't fall naturally in the key, although all you're really doing is using a major 7th, but there is no Gb7 in Db major. The whole idea behind saying "I-IV-V" changes, are that they are within the key. Someone names the key, says the changes are "I-IV-V" and since you know your scales, you can derive the chords you need to play. Does that make sense?

[JWC]

Yes Jazzbo that makes good sense to me. I had a feeling that was how it was but I wasn't sure. So chords of a song are generally made up of notes within the key of the song (unless a KEY change). Thanks dude.

[David Kaczorowski]

Originally posted by JWC
yeah, well when you go from I to IV to V, are you changing keys??

Traditionally, no; but if you're refering to I-IV-V in a blues context where each of those chords is a dominant 7 chord, technically, the answer is yes.

Jazzbo gave you a really good answer. The implication is that what the chords specifically are signal whether there's a key change or not. You really have to have a good foundation in harmony to understand. There's no easy explanation.

[Rockinjc]

It always depends. If the song was written as diatonic, then you don't chage keys, just the note you start on. The chords are just every other note in the scail of the songs key starting on that degree. Thats why the V chord is often a seventh chord instead of a major seventh.

Lots of folks don't write diatonicly though and for years I got away with more or less changing the key that I play in against the song and playing a new scale as if that was the new key instead of a chord in the origianal key. It doen't help to play diatonicly if no one else is.

I think the main reason that a lot of good songs go diatonicly is that it sound nice. A bonus is that others you are playing with can quickly come to a consensous about what is going on in the music. If everyone knows what key is used it helps to predict the chords, and can help in seeing the chord progression and what notes to play on bass.

Hope that helps,
jc

[jazzbo]

Well you certainly don't have to write diatonically. It's like Dave said, it takes an understanding of harmony. The idea is most pop music is to still resolve to something, somewhere. It's just more pleasing to the ear. Generally, in popular music, this is what wants to be heard. As Dave mentioned, often I-IV-V changes may be played as all Dominant7 chords. The IV and I are not dominant in the diatonic context, but it still resolves. The dominant V chord, of course, resolves quite nicely to the I chord, and the minor 7th of the IV played as dominant does resolve to the V of the dominant V chord.

I guess my point is, you don't have to have everything within the diatonic scale, but you should understand some harmony to make sure the chords resolve.

[David Kaczorowski]

Originally posted by jazzbo
often I-IV-V changes may be played as all Dominant7 chords. The IV and I are not dominant in the diatonic context, but it still resolves. The dominant V chord, of course, resolves quite nicely to the I chord, and the minor 7th of the IV played as dominant does resolve to the V of the dominant V chord.

Mmm, yes and no. In a basic blues you're dealing with I7-IV7-V7. Well what is this I7, it's really the dominant of the IV. It resolves to the IV7 in so much as the tritone (defining characteristic of dominant chords) resolves, but the chord it resolves to is a dom7 with it's own tritone wanting to resolve. When the IV7 goes back to I7, the tritone doesn't actually resolve, it moves. Same thing when I7 goes to the V7. This is just an example, I don't have time to think about it all in detail right now. But even at the end of a blues, it doesn't resolve completely, as it ends on a dominant chord.

[jazzbo]

Good point.