Subtle-t said:
I have read through plenty of music theory guides and basic guides on notes/chords/scales, but I want to know how chords and scales interact within the same song.
Let me preface this with... Don't stop at Diatonic Theory, or you'll be back on this forum telling everyone how restrictive music thoery is. Diatonic theory is just the beginning. Also, what you're asking is too broad to answer completely in one post. But here's a good start...
Every scale has a set of diatonic chords. And each like scale has the same pattern of chords. A major scale's diatonic chords will always follow this formula: IMaj-iimin-iiimin-IVMaj-VDominant-vimin-viidim. In the key of C: Cmaj-Dmin-Emin-Fmaj-G7-Amin-Bdim, and those chords are diatonic to C major because they are made up exclusively of notes in the C major scale.
Diatonic theory says you can play any C scale note over any of those chords and get a consonant sound. Those same notes are also found in the modes of C major: D Dorian, E Phrygian, F Lydian, ect. So, playing D Dorian, for example, over Dmin works the same.
But remember, don't stop at diatonic theory. Feel free to play any note over any chord as long as it delivers a sound you like. Learning how the non-diatonic tones can color your harmony is essential.
Try searching the net for "diatonic chords" and you should find a better explanation of my brief introduction. Once you feel comfortable with diatonic theory, try searching for "chord alterations", "color tones" and "chromatic tones".
Subtle-t said:
Also, what are some common chord progressions used in hip-hop.
I disagree with PlanetHitz on this. I feel chord types are partially responsible for the sound of some genres. The rhythms used when playing those chords play a bigger role, but...
Hip hop samples lot's of old r&b, soul, funk and jazz. R&B, soul & funk are all fairly simplistic, rarely using chords extended past the 9th. Typical r&b & soul chords are: major & minor triads; major & minor 6ths; major, minor & dominant 7ths; major, minor & dominant 9ths.
Funk tends to use a lot of dominant chords: 7ths, 9ths & an occassional 13th.
Jazz uses pretty much every chord, but what makes it really sound like jazz are the alterations and extentions. Jazz musicians tend to use a lot of altered dominant chords: b9ths, #9ths, 7b5, 7#5, ect. And jazz musicians use the larter extentions on a regular basis: major, minor & dominant 1ths & 13ths.
Typical progressions: I-IV(C-F); I-V(C-G7); V-I(G-C); I-IV-V(C-F-G); ii-V-I(Dmin-G7-C); vi-ii-V-I(Amin-Dmin-G7-C). Try the minor version as well: i-iv; i-v; i-V... And try searching the net for "common chord progressions". You'll find these and more.