Conversation so far:
What was special about Mal Waldron's artistry?
Before his breakdown, Mal Waldron played in a lyrical way, but after that he couldn't find that lyricism inside himself and became a very angular player.
What instrument did Mal Wauldron play?
Mal Waldron played the piano.

Question: What was lyrical about his playing?
Self-contained rewrite: What was lyrical about Mal Waldron's playing?