Thanks, Bernhard,
Let's see if I am understanding what you're saying..
Are you doing something like this?
Left hand: CEG Right hand: C
Left hand: dfa Right hand f
In other words, playing the triads with the left hand, and playing a melody using one of the notes in the triad with the right hand?
Yes.
You can actually play anything you want on the right hand
as long as you restrict yourself solely to the notes of the scale you are using.
The progression I-IV-V-I will always fit any melodic extemporisation. This has several advantages:
1. It teaches the student the three most important chords (I-IV-V) for all scales.
2. It trains the student move smoothly between the three chords.
3. It teaches hand independence, since while the left hand is moving in a steady, unchangeable way, the right hand is weaving a melody around the chords, with rhythmic freedom.
4. It teaches the student the notes of the scale, since s/he is only allowed to use those notes.
5. It gives the student a taste of free improvisation.
6. It gives the student the opportunity to experiment and get to know the several degrees of the scale (for instance you can limit the right hand melodic notes to be only the mediant, the submediant and the leading note).
7. It is a SUPER-FUN way to get acquainted with chords and scales.
8. After a 10 – 15 minutes instruction the student is actually “playing”, and some of the tunes they come up with can be quite impressive – specially after they overcome an initial shyness and realise that they cannot go wrong, since as long as they keep to the notes of the scale, it will always sound good.
9. It teaches the importance of the tonic – since if it starts to sound wrong, all you have to do is return to the tonic. You can use it to experiment with different melodic patterns: smooth ones where the intervals are small, or jumpy ones where the intervals are large.
10. There is something very “meditative” and satisfying about this sort of extemporisation
This if course is just the start. You can complicate it in many ways: You can use more complex chord progressions (I often use this exercise using the same chord progressions of the piece the student is learning). You can use different rhythm patterns on the left hand. You can modulate.
Consider this: If you do this on C major, and use the C-F-G chords in the left hand and restrict the melodic notes to CFG on the right hand (tonic – subdominant-dominant) you will get a certain effect. If you now change the left hand to Ab major (Ab-Db-Eb triads) but keep the right hand on CFG, (they are the mediant, submediant and leading note of Ab major), you can demonstrate in a dramatic way the ideas of scale degrees – and why they are important – as well as the idea of tonal centre and modulation as a way to shift the tonal centre.
As you can see, there is really no limit to this approach, which of course is not new. It is the beginning of improvisation as practised by most pianists in the 19th century.
Best wishes,
Bernhard.
Topic: What primary chords, I IV, V or I IV V7?