You can assign instruments to solo and section players as well as to ensembles.

In Dorico Pro, you can assign multiple instruments to solo players, as solo players often play multiple instruments, such as an oboist doubling the cor anglais.

Before you can assign instruments, you must add players or ensembles, which may in turn also be assigned to groups if needed. If you add ensembles, it is by default not necessary to add any instruments, since these are already included when you select the type of ensemble. However, you can add further instruments to ensembles.

Instruments in Dorico Pro do not have limited ranges; it is possible to notate any pitch in any register on every instrument. However, in the piano roll editor in Play mode, only pitches that fall in the MIDI note range 0-127 can be represented. Similarly, if you input a pitch beyond the range of samples in the assigned VST instrument, the pitch does not sound in playback.

You can always change the initial specification and add or delete instruments.