I have to disagree,I find baritones sluggish for song accompaniment, and therforea bit limited,they were originally used for playing baritone parts in concertina bands.
I find the treble the most useful for song accompaniment, as does Louis Killen,I believe K KENDRICK andDBarber use48 trebles.Steve Turner [i think ]mainly uses a BassBaritone.
I do occasionally use a tenor treble,but mainly for adding parts on recordings.
I would advise a 48 key treble,for song accompaniment,it is light,and therefore easier to play with gusto,it can be played effectively for sad songs as well.
sometimes it is very effective ,if the singer is a baritone to have a contrasting sound, rather than more baritone sound.
but still what would I know about it. Dick Miles