Complex sentence: Laiho wanted to make use of the keyboards more effectively, though Pirisjoki was not attending rehearsals; thus, he was fired and replaced by a friend of Raatikainen's, a jazz pianist named Janne "Warman" Wirman.
Split into simpler sentences: Laiho wanted to make use of the keyboards more effectively, but Pirisjoki was not attending rehearsals. Thus, he was fired and replaced by a friend of Raatikainen's, a jazz pianist named Janne "Warman" Wirman.