In, for example, the C major key, the available tensions for the C major seventh chord are 9, 13, because:
Harmony 3 - Berklee, Barrie Nettles, p17:
For diatonic chord progressions, available tensions and other non-chord tones will be diatonic.
Harmony 3 - Berklee, Barrie Nettles, p15:
Available tensions are non-chord tones which are a whole-step above a chord tone (a major ninth reduced by an octave).
Which means there are other available tensions, just non-diatonic. i.e., for a C major seventh: 9, #11, 13. But the #11 is flat out denied "available tension" status by some sources:
Secondary dominants - aucklandguitarschool.co.nz:
“Available tensions” are non-chord tones that are diatonic and a major 9th above a chord tone.
Anyhow, if I would assume that available tensions do include the non-diatonics, what would I call them as a whole to minimize ambiguity? All available tensions? Chromatic tensions? NCTs that are a major 9th above a chord tone?
And so, just to clarify, would one use a non-diatonic available tension in a non-diatonic chord progression?