Dorico 3 has revolutionised the way automatic player labelling is done by the condensing feature but if you’re stuck on Finale, Sibelius or any other you have to label your staves like a caveman.
Say you’re writing your score in a condensed way so what two flutes share a staff. This staff should then be number like the picture below for example.
Notice then that when the two flutes or oboes play unison the entry is marked ‘a2’ meaning both the players sharing the staff will be playing this line.
If the two flutes play similar lines the parts should be written in two voices and any common rests should only be shown once.
It’s still crystal clear that both flutes are playing this line. The double stems on the initial note also makes the ‘a2’ indication redundant.
If the two parts are fairly similar this can still be shown with respective rests in each voice.
The next example is from 4 horns. 1 and 2 share the top staff, 3 and 4 share the bottom. The numbers indicate which of the instrumental parts have the music written. The numbers won’t be shown in their parts and their music will not be shown in the parts of horn 2 and 4 (unless it’s crucial as a cue).
In the last example the second trombone is momentarily more easily condensed with the lower brass instead of trombone 1. This is simply indicated like this:
I try not to condense more than two similar instruments but if you do have 3 horns sharing a staff but only two horns playing simply writing ‘a2’ is not sufficient. You have two specify which two are playing by writing ‘2. 3.’ for example.
You never write tutti, unis. or anything other than ‘1.’ ‘1. 2.’ ‘a3’ or something to that effect.
‘Div.’, ‘tutti’ or ‘unis.’ is only a section term and is never used for wind instruments since it is not a section that is split, rather the staff is a condensation of two similar instruments.