In the last couple of lessons we have been focusing on building chords and definining tonality. As sax players, we don't play chords but as you discovered in the last lesson, we can define a chord by outlining its' qualities.
You won't hear a one chord tune. This is because a single chord, although great in a moment, is not sustainable in order to keep a melody interesting. This is where chord sequences come in. The idea behind a chord sequence is that it strings together chords, often (but not always) in the same key to enhance a mood or to add contrast by introducing a different mood.
Let's refer back to lesson JS102. In that sax jazz lesson you'll remember that we took all of the notes from the scale of C major and used these to create a set of chords. Hopefully you can remember that by using the scale of C major we can create several chords:
Chords I, IV and V were Major Chords
Chords ii, iii and vi were Minor Chords
And chord vii was the odd one out (this chord is what we call diminished and has a similar function to the V chord)
So, if let our inner composer out and we are trying to create a piece of music in major key that sounds bright and happy it would make sense to use a few of the chords from that key that provide that sound. We already know that Major chords give the bright and joyful sound so we would use a chord sequence that uses those chords. Our three options for this kind of sound are chords I, IV and V.
Certain chords have a certain sound as I've mentioned before but also certain chords are used as a function to pull the music naturally into other directions. The main reason for this is because of the pattern of tones and semitones the major scale we have used. The semitone movement between E->F and B->C naturally pull the chords in certain directions and it is this that creates our natural, or good sounding, chord sequences.
Simply put, a chord sequence is literally staying on one chord for a while then moving onto another chord for a while.
Let's create a chord sequence. It would make sense to start with a C chord if we are in the key of C as it is the "home" sound. This home sound will give us a strong finish and also set up our ears to be receptive to C major sounds. We could try moving from chord I to IV, V and then back to I to finish. Check out the video to hear how these work in practice and actually listen to the function of each chord.
I -> The HOME chord, sounds finished when C is the lowest note in the chord. This chord is known as the Tonic.
IV -> You can use this to create an ending by moving back to I but also takes you nicely to V perfect 4th up or 5th Down from the I chord also called the subdominant.
V -> Contains a natural pull to the I chord especially when it contains a 7th. You can almost guess where it moves next without hearing the following chord. This chord is called the "Dominant". Root moves up a perfect 5th or down a perfect 4th from the tonic.