[Update: the book is Fool's Run by Patricia McKillip!]
Dear Internet, please help me find a poorly-remembered book!
It was scifi, likely published in the 80s but conceivably late 70s or early 90s. I do not remember much of the plot but I remember that there was a playing card motif and I think also a harlequin motif.
The most distinctive feature I can remember is that there was a virtuoso pianist who would occasionally go into a fugue state; I believe he was one of the main characters.
After ruminating on this further, I've added a few other qualifiers:
1. IIRC, the pianist is vaguely implied to be a reincarnation (either natural or technological) of Beethoven—or at the very least has a particular fascination with his works.
2. I think one of the characters is a red-haired woman? (I appreciate that this doesn't really do much to narrow things down when it comes to speculative fiction.)
3. It was very much a scifi book, not fantasy. Parts are set on a space station, I think.
The book I was looking for was Fool's Run by Patricia McKillip. After reading it over the last couple of days, I’m not at all convinced that I ever finished it the first time through. But I finally understand why I started reading it in the first place: I must have checked my local library for other books by McKillip after finishing Riddle-Master.
Thanks to @spills, @otterly_icy, @librarianknight, and @CliftonR for answering a question that's been plaguing me for over a decade!
I have a copy of 'Fool's Run' right here! I haven't read it in a long time, but from the back cover blurb:
'... Seven years later: a bar-band pianist named The Magician suddenly plays Bach, while a riot burns around him. The Queen of Hearts, a drifter who hides her life beneath a golden mask, steps enigmatically from the shadows. [Prison] administrator Jase Kiyose unexpectedly lets a concert bring sound to his silent sterile hell. ...'
Does this ring any bells?
I flipped to the first chapter - it begins with the pianist coming to from a fugue state he's been in for most of the night, playing Bach non-stop, and there seem to be some Tarot motifs as well as playing card motifs, so I think this has to be the one you're looking for.
@CliftonR Yep, Fool's Run is the current theory! Now to find a copy, since it doesn't seem to exist in ebook format.
@jwisser @spills @otterly_icy @librarianknight
Glad to have helped!
I don't remember very much about the plot, but I do remember thinking it was interesting because while it is clearly SF, McKillip wrote it very much in the /style/ of fantasy and using fantasy tropes.
I was going to write that that was her only foray into science fiction, but on investigating I was reminded of Moonflash, which is also SF.