Haha yes there is a finite amount fortunately! There are only 4 altered tensions. I explain I categorise them below.
In addition, by memorising the 4 simple UST formulas we can drastically reduce the amount of information that we need to remember to access the more complex altered dominant sounds in all 12 keys.
Yes I find that a very useful way to look at harmony. Just as a painter can choose different shades of a colour in a painting, we can also choose different shades in our voicings.
When playing a new voicing with specific extensions and/or alterations, I recommend to stop and look at the notes we’re playing and say to ourselves, for example, “that’s the b9th” and then play that b9th again to hear what it adds to the ‘colour’ and ‘flavour’ of the voicing and in context of the progression.
We can do the same with every other alteration such as #9/#11/#5 which is specifically what we are addressing in this practice series.
By doing this, we gradually build an awareness of what those tones sound like so that we can make more informed choices on when to use them in our playing.
To take this point further…
Once this information has been absorbed, we can start to think in terms of ‘colour’, ‘texture’, and ‘flavour’. This might sound a but whacky but let me elaborate…
A dominant 7 b9 chord sounds the same in every key, not in terms of pitch, but in terms of the ‘colour’ and ‘texture’ it creates. Play a simple voicing for C7b9 (C-E-Bb-Db) and then the same for F7b9 (F-A-Eb-Gb) and you will hear that each chord elicits the same ‘mood’.
I’m sure we all hear alterations differently, but for me, they have the following characters:
The dominant 7 b9 chord has a somewhat soft and subtle character
The dominant 7 #11 chord has a mysterious, floating, lingering character
The dominant 7 #9 chord has a jarring and abrupt character
The dominant 7 #5 chord is somewhere in between the b9 and #11, subtle, but has a floats and lingers
This is the same in every key.
Of course this is just single alterations. When we combine these tensions using Upper Structure Triad Vocings, the sounds become more complex, but I find the above distinctions to help me when arranging tunes and deciding what tensions to add to my voicings based on the kind of mood I want to create.
Have fun playing around with this stuff!