I think this all depends on personal tastes-- I have had clients listen to Pearl Jam and , Metallica, self recorded protest songs- that she sang along with, Heart, bagpipes-- to name a few
personally I like Santana because they have long sets that move along the lower body-- I saw Carlos talking about their music one time and he said they watch the women they are looking for ( indicated by gesture) a sensual response from women-
belly dancing music, it is a good idea to have soothing and stimulating music because often women need some pepping up or activity while laboring and too soothing can be counter productive.
singing can help some women and things that were sung to you as a baby or child are well memorized and easy to do without thinking much... rock-a-bye-baby, baby beluga, itsy bitsy spider...