How broad should my niche be?

I am considering how wide or narrow my niche should be for my new business. I already run the Alameda Cello Academy, which caters to classical music students of all ages and levels. I want to broaden to bring in adult amateur students that want to learn improvisation, a totally different skill than classical music, which is mostly what I teach at ACA. How broad should my niche be? I would like to offer this for women who are cellists with some amount of technical facility on the cello who want to learn to play music that is more fun for them than classical, so pop and jazz and ethnic music. But is that niche too small? Is it a bad idea to cut out half…men? I could include them as well…also, is it too narrow to offer this to amateur cellists? Should it maybe be all cellists? Women Cellists of Improvisation? Goddesses of Cello Improvisation? Any ideas? Thanks!