Como vocalista ha trabajado para King Crimson ("Lizard", 1970), Johnny Harris ("All To Bring You Morning", 1971), Vangelis ("Heaven and Hell", 1975), Alan White ("Ramshackled", 1976), Rick Wakeman ("1984", 1981), Mike Oldfield ("Crises", 1983, y el tema «Shine», 1984), Giorgio Moroder ("Music From The Film" Metrópolis, 1984), John Paul Jones ("Music From The Film" Scream For Help, 1985), Tangerine Dream ("Music From The Film" Legend, 1986), Stanislav Syrewicz ("Music From The Film" Biggles Adventures In Time, 1986), Gowan ("Great Dirty World", 1987), Toto ("The Seventh One", 1988), Jonathan Elias ("Requiem For The Americas", 1989), Kitarō ("Dream", 1992), Charlie Bisharat ("Along The Amazon", 1993), London Philharmonic Orchestra ("Symphonic Music of Yes", 1993), Ayman ("Dancing with My Soul", 1994), Milton Nascimento ("Angelus", 1994), Cielo y Tierra ("Heaven And Earth", 1996), 4Him ("Streams", 1999), Steve Howe ("Portraits Of Bob Dylan", 1999), Béla Fleck & The Flecktones ("Outbound", 2000), Eduardo Marquez del Signore ("Captivated", 2000), Carvin Knowles ("In Elven Lands / The Fellowship") y Dream Theater ("Systematic Chaos", 2007), Peter Machajdik ("Namah", 2008).