Complex sentence: After several name changes and a successful U.S. tour, the trio grew into a quartet of semi-permanent musicians, mainly European Rock-A-Billy musicians who play full-time in other bands of this genre.
Split into simpler sentences: After several name changes and a successful U.S. tour, the trio grew into a quartet of semi-permanent musicians. Mainly comprised of European Rock-A-Billy musicians who play full-time in other bands of this genre.