10 February 2017
Written by Buster Birch
When playing jazz it is important to be able to transpose your phrases/motifs/melodies/licks/ideas and to help enable this we always relate the melody note to what chord it is on/under/over/with and not the key signature, as tends to be done in classical music theory or analysis. So if you play a G on a G7 chord it is identified as a 1 (the root note of the chord/scale) but if you play a G on a C7 chord it is identified as a 5 (the 5th note of the chord/scale) no matter what the key signature is. This can take some getting used to and demands that you are very familiar with your scales but it can be extremely useful and, once fluent, enables you to make sense of your melodic phrases and then transpose them to any key or other similar chord progression.
In jazz theory the chords are often referred to by roman numerals, relative to a key centre, which may or may not correspond to the key signature. Again this can take some getting used to, but is extremely helpful when transposing and also making sense of the harmony. It helps identify the "function" of the chords. It also means that everyone in the room is talking about the same thing, whether or not they are playing a transposing instrument.
Reading and understanding chord symbols is an essential part of playing jazz. They are a short hand way of implying a lot of information quickly. As with any new language it can take some time to become fluent. When describing chords and scales jazz musicians often refer to flattened this and sharpened that. This is always relative to the major scale. So, you need to be absolutely fluent in all 12 major scales, so that then you can relate the alterations of the other scales/chords to the fundamental sequence of the major scale. For example an Am7 chord would imply an A dorian mode which we describe as having a flattened 3rd and flattened 7th. These alterations are relative to the major scale. Therefore an A major scale (A, B, C#, D, E, F#, G#) with a flattened 3rd and 7th becomes A, B, C, D, E, F#, G, which is A dorian mode, which can be used on an Am7 chord. In order to make the alterations you have to know your A major scale first. Therefore it is extremely important that you are very familiar and fluent with all 12 of your major scales, so you can then start using them as a basis to describe/think of the other altered scales and modes.
Did I mention... Learn all 12 major scales! Make sure you are fluent. Think of them numerically (1, 2, 3, 4, 5, 6, 7) in each key. Don't just think of the letters. Think about what number/degree of the scale it is. When you are in G major an F# is 7. When you are in D major an F# is 3. When you are in A major an F# is 6... etc, etc, etc...
It takes time to become fluent in this way of thinking, but with regular daily practice you can do it. You can practice thinking anywhere and at any time! So make use of your "down" time. Once you are more fluent in this way of thinking then understanding how jazz works becomes much easier.