Another take:

https://youtu.be/wxyGTLZVuyY

1980, Soundtrack from Serial

A Changing World, Main Title
https://youtu.be/311SVhy5Rd0

A Changing World, 3:18 version
https://youtu.be/T4H4uPGtoKc

A Changing World, End Credits
https://youtu.be/V3zF3YikJi4

https://youtu.be/MuHe6iEqEjk

Backstage interview with Give Me Wings
Performance: I Will Whisper Your Name and The Moon is Still Over Her Shoulder

I've had the Riversong album since around 1981 or 82, and have never been totally sure which lead vocals are Michael, if any. Some sure do sound like him, particularly Full Moon Of April and Places And Old Friends. I notice your audio samples don't indicate that any leads are by Michael, just Mark. Can you provide more details? Thanks! Bill

Michael Johnson - Roller Coaster Run (single version) RARE - YouTube
This version from the RCA 7' single in the USA was only released once on CD - on the compilation called "Life's A Bitch" in the UK and Europe.
Michael Johnson – Life's A Bitch (1989, CD) - Discogs

Michael's great theme song from the movie "Serial" in early 1980. 
(2) Michael Johnson - A Changing World (stereo master 1980) RARE - YouTube

Michael's theme song from the soundtrack of the movie "Serial" (1980)
https://www.youtube.com/watch?v=weIqCfye6qk

https://youtu.be/bCnFPCPd1r0

https://youtu.be/Hkr5nCr3XH0

Songs: Roller Coaster Run (Hugh Prestwood), Drops of Water (Bill LaBounty, Roy Freeland), That's That (Prestwood)

https://youtu.be/dpOukz6QwiI

horribly out of sync.