Overall, it's a smorgasbord of sound. Some jazzier themes, some orchestral themes, some rock themes, some Wild Arms sounding tunes, some Japanese inspired sounds, etc.
Chiba's themes are mostly jazzier and orchestral related. Kudo does a bit of the Wild Arms sounding stuff, some rock, some orchestral music, some Japanese sounding themes, and some of the jazzier tunes. Abe mainly does orchestral and rock tunes, Iwata does some Japanese inspired tunes and an orchestral theme.
If you go to the album page on the Basiscape website, you can hear 5 different samples:
http://basiscape.com/store_majikoi.html First and last by Chiba, middle 3 by Kudo.