8.2.6 Instrument transpositions (in lily 2.6.4)

[Frédéric Bron]

I have spent some time to understand what should be the pitch in 
"\transposition pitch". In particular, I found difficult to understand 
what octave to use.

I would like to propose to add a comment that could be something like:
"The pitch that should be given to \transposition corresponds to the 
real sound heard when a c' written on the staff is played by the 
transposing instrument."

Frédéric