Pitch and intervals are so interesting. (I won’t relegate rhythm to a lesser status, just musing with pitch as all good brass whisperers do.)
Many of the just intonation pieces I write have a different ‘tonic’ or reference pitch from each other. This makes preparing a large set up of pitches in the music software (Dorico) time consuming for each work. The issue with making a large set is deciding which pitch will be the reference and minimising the complexity of the calculation of notation symbols and divisions of the tones and semitones for microtonal playback.
Part of the idea is to minimise the number of combined accidentals (pitch modifiers) on the staff.
Another aspect is to make any reference pitch close to a standard Hertz reference (A=440, Bflat = ? etc). This is less of a problem since Dorico notation software can alter the pitch by Hertz.
Preparing for my work in 2020 I have set my reference pitch at G. This is not in deference to Harry Partch, but rather to help horns and strings have a good combined starting point. I did consider A, which is what Marc Sabat did for his work on microtonal horn writing in combination with strings, which has the advantage of the standard tuning note being the reference. His work 'Towards an Expanded Definition of Consonance: Tuneable Intervals on Horn, Tuba and Trombone (2006)' with Robin Hayward and '23-Limit Tuneable Intervals above and below A (2005)' show extensive possibilities.
For my purposes at the moment G is also a note that all standard orchestral strings use and is only 3 perfect 5ths in the chain from F and one more from Bflat. These are the easiest reference notes for tuning on the horn. After some experiments it seemed easier to work from a simple note name, one of these: A B C D E F G. The chain of 5ths sees these as F C G D A E B. Both G and D are in the centre. I chose G because it is one 5th closer to Bflat and Bflat is also an important note for other brass instruments as well as clarinet. By the way, the composition I am working on at present has a 'tonic' of D, the only adjustments I am making to the notation of the score is to show any tunings with cents with D as 0 cents and G as -2 cents even though the notation is based on G as 0 cents and D as +2.