Part black/white, part color movie

[DerGolgo]

I'm trying to identify a movie I only ever saw maybe half off ... over a decade ago. And I wasn't entirely sober, either.
But I would like to see it in it's entirety.
Here's what I still recall about it:
It was part in black and white, part in color.
The protagonist, somehow, traveled to the moon. Scenes on Earth were b&w, scenes on the moon in color.
I think the protagonist was a concert pianist of some sort, he somehow managed to drop back to earth right into a performance.
I think there were a few scenes set on a train.
For some reason, for many years, I'd associate the song "Arthur's theme" with this film. That whole line about "If you get lost between the moon and New York City" came close enough to the plot of the movie in question. But it absolutely WASN'T Arthur.
Judging by the film's looks, it was maybe from the 1970s or 1980s. If it was older, it wasn't by much.
I cannot recall any cast, except that a) a few were familiar faces, I think, and b) at least one moderately famous actor was in it. For some reason, I was convinced for years that it was Walther Matthau, but I've already looked over his imdb page, that conviction appears fallacious.

I'd greatly appreciate any help in figuring this one out...

[Ag0stoMesmer]

Nothing Lasts Forever (1984)?
Criticker link

[DerGolgo]

YES! I recognize that title!! Thank you!!!