Most recordings you own by a single artist, group, or composer

That was the band Frank used for Overnight Sensation. Yes Ralph Humphreys on drums. I've got to say, though, I probably listen to Hot Rats the most.

The Czech Philharmonic Orchestra (a sound that is slowly disappearing from the world), and the Paris Conservatoire Orchestra (a sound that has long since disappeared from the world).  We won't hear their like again.  Ditto for the old Soviet-era Russian orchestras.  These groups typified a more colorful, organic style of playing that modern internationalized and standardized conservatory training has just about eradicated.  I sorely miss those sounds, and try to collect every decent example of them ever recorded....which has been a huge but enjoyable pastime of mine for decades.

Zappa for me as well.  Tostadounitos and Richmos, I do love that particular Zappa band, but I love them all (like my kids I guess?).  The relative sloppiness of Bongo Fury (with Frank flubbing the beginning of "The Muffin Man" and Captain Beefheart, ... just being Captain Beefheart, has never kept me from enjoying the album, especially the closing line.  And picking a favorite band means I'd have to skip some singularly great players (Vai, Bozzio, Chester, etc.).  One of the things I love about Frank is how much the personalities/talents of the band infected the music, despite Frank's singular vision and reportedly iron grip.  I'm thinking not only of Bongo Fury, but also Live at the Filmore/Just Another Band with Flo and Eddie, Live in NY with Don Pardo and Bozzio's flourishes, and anything with the Ikettes singing back up.  I do so miss him -- now, especially.

Tony Rice

Is there ever such a thing as TOO many albums to own?... Hunting vinyl has been a passion since I was 13 and had to fight my mother for ownership. (Not as bad as it sounds, but it was still an event.) 
I don't have actual counts, but
Miles Davis >30
Bill Evans >40
Duke Ellington around 50±

There's no such thing as too much Duke!