Timothy Lanfear supplied a simple understandable way of achieving my aims. I was thrown headlong down the route of trying to modify the sequential music stream as was done for indicating/modifying pitches outside the “range” of each instrument. “range” being somewhat arbitrary as it depends on the skill of the musician. This employed range data in the scheme process and input instrumentname from the lily source file
Appropriate clef and transposition can be easily provided entirely in Lily data rather than fiddling about with the music stream.
The solution provided answers my immediate needs. Thank you very much all.
Ps \inherit-acceptability is new to me I will have a search in the manuals.