Hi Joe

The only problem I see in using tetrachords as a basis for solos is that your focus will still be on pre-determined blocks of notes that you consciously impose on the material you're playing, albeit ones of smaller length.

The issue is that improvisation isn't just about using conscious strategies or pre thought ideas/notes to fill in or delineate the harmony of the moment so much an attempt to expand on the direction the tune is taking intervallically and in terms of important target points of resolution and of course it's all important emotional properties. This is the total structure of the tune that you have to get down and its a far more organic and liberating strategy than dividing up tunes into chords and scales that you deal with in isolation.

Often with the latter you often get results that are obsessively focussed on patterns, disjunct in terms of melodic and rhythmic flow of ideas and a feeling of the improvisation not 'breathing' or flowing naturally out of the tune. Knowing the deeper structure and properties of the tune allows your subconscious free reign and the possibility of surprise or spontaneity to make itself felt in your 'choices' for want of a better word. It's actually the music itself that 'chooses' at this point.

Another thing about tetrachords. Due to the fact they are constructed mostly in half or whole steps it can limit your view of the fret board and if you're looking to expand your awareness of all the intervals it would be better to internalise the basic scales as others have said. Then you can learn all the 3 and 4 note combinations the scale plays through. Play them and hear them over and over sequencing them throughout the scale and you'll develop a palette of interval moves your ear and memory guides you towards quite naturally of having to think about it.

The only problem is that this stuff never leaves you and it still becomes a 'muscle memory nervous tic' as it were. This can be variously viewed as a 'personal signature' or a limitation depending on how you view improvisation.

For me improvisation is best when you're not looking to play something that isn't suggested by the melody. it's about opening yourself up to tune letting it and your emotional response dicate the direction of your playing as much as any analytical standpoint.


Regards


Alan