Here are the classically-oriented labels I've listened to on rdio. Quality may not be highly correlated with popularity, of course. And rdio has no musical genre tags, so for example, the Nonesuch count includes Wilco and Ben Folds/Nick Hornby.
Wilco via Wikipedia
- Nonesuch (1,300,000 listens)
- Sony Classical (444,074)
- Decca (243,756)
- EMI Classics (196,522)
- Nonesuch/WBR (107,643)
- DG (71,008)
- Signum Records (64,370)
- Orange Mountain Music (14,856)
- Readers Digest (10,258)
- EMG Classical (5,227)
- Naxos (4,834)
- Cedille Records (4,205)
- New Albion Records (3,772)
- Albany Records (3,175)
- Sub rosa (2,515)
- Stradivarius (2,205)
- Cantaloupe Music (1,100)
- Materiali Sonori (1,025)
- Mark Records (521)
- Ionik Recordings (471)
- NWCRI (430)
- OMAC Records (352)
- New York Philharmonic (349)
- New Amsterdam (321)
- Wergo (286)
- American Symphony Orchestra (229)
- Starkland (145)
- NMC (129)
- Innova (38)
- Virtuoso Music (20)
- Somm Recordings (16)
- Composers Concordance Records (12)
- Pogus Productions (9)
- Bulgarian National Radio (6)
Update: additional labels
- Alia Vox (14,329)
- Chrome Dreams (6,437)
- Genuin (250)
- Acheulian Handaxe (22)