To my ears, Mal Waldron was, like Andrew Hill, and Horace Tapscott, a player who (in his own compositions at least) tended to take a simple motif and explore it in many subtle variations, as opposed to basing lines off complex harmonic changes. Rhythmic displacement and use of space are evident elements in his playing. All three players shared a similarly dark sound and percussive touch. Waldron recorded recorded albums of standards and albums featuring original tunes and spanned a gamut from inside to outside in the process.
Three I particularly like:
Seagulls of Kristiansund
Left Alone '86
You and the Night and the Music
He and S. Lacy were buddies and recorded several times together, for those who enjoy Lacy.
.