Conversation so far:
Was Buck Clayton a mainstream musician?
Buck Clayton was a leader of mainstream-oriented jam session recordings
When did Buck Clayton's music become mainstream?
Buck Clayton was a leader of mainstream-oriented jam session recordings in the 1950s.
Were these Buck Clayton mainstream-oriented jam sessions well received by critics?
Buck Clayton “synthesized much of the history of jazz trumpet up to his own time, with a bright brassy tone and an apparently limitless facility for melodic improvisation”
What did it mean for Buck Clayton to be a mainstreamer?
Critic Stanley Dance coined the term mainstream in the 1950s to describe the style of those swing era players like Buck Clayton who fell between the revivalist and modernist camps.
Was Buck Clayton one of the artists that fit into this category?
Buck Clayton was precisely one of the players to whom this appellation most applied.

Question: How did he feel about this label?
Self-contained rewrite: How did Buck Clayton feel about this mainstream label?