Complex sentence: He would later join Neil Finn on stage for some of his solo concerts supporting Finn's Try Whistling This (1998) before rejoining Supertramp, producing for Tim Finn and releasing his own work (Nada Sonata, 2002).
Split into simpler sentences: He would later join Neil Finn on stage for some of his solo concerts supporting Finn's Try Whistling This (1998) but would also rejoin Supertramp. He continues to work with Supertramp as well as producing for Tim Finn and releasing his own work (Nada Sonata, 2002).