Conversation so far:
What is Leaving Basie?
Young left the Basie band in late 1940.
Why did he leave?
He is rumored to have refused to play with the band on Friday, December 13 of that year for superstitious reasons spurring his dismissal.
How did he react to his dismissal?
CANNOTANSWER.
What did he do after he was dismissed?
Young accompanied the singer Billie Holiday in a couple of studio sessions (during 1937 - 1941 period) and also made a small set of recordings with Nat "King" Cole.
What did record with them?
His studio recordings are relatively sparse during the 1942 to 1943 period, largely due to the recording ban by the American Federation of Musicians.
Did he work with any other artists?
he recorded some sessions for Harry Lim's Keynote label in 1943.
Are there any other interesting aspects about this article?
In December 1943 Young returned to the Basie fold for a 10-month stint, cut short by his being drafted into the army during World War II .
What happened after he was drafted?
Recordings made during this and subsequent periods suggest Young was beginning to make much greater use of a plastic reed.

Question: Why did he change to a plastic reed?
Self-contained rewrite: Why did Lester Young change to a plastic reed?