When it comes to artists like Thelonious Monk the words normally used to describe musical innovators don't seem to fit quite so well, so quirky was his style both of writing and playing, ( and his taste in hats )
He was neither a vocalist nor a lyricist. Was he a songwriter? it's debatable........and, in a way, irrelevant. His compositions have been more aptly described as ' canvasses ' set up for himself and other musicians to experiment with. But to a jazz layman like me his name will always be associated with one of today's best-loved jazz standards, "Round Midnight" , a composition which just oozes the melancholy of lost love, ( probably through a haze of alcohol ). Monk had a collaborator in the creation of this treasure, a trumpeter and band leader called Cootie Williams, who played a leading role for many years in the Duke Ellington Orchestra. And those wonderfully evocative lyrics were added by Bernard Hanighen.
Monk wrote several other numbers which have since become well-known in jazz circles, such as "Straight No Chaser", "Off Minor", "Skippy" and "Mysterioso". All wordless and mostly quirky, numbers like these represent the creative essence of Monk. And yet he was quite capable of writing in a far more conventional style. For example, a number such as "Ask Me Now", if provided with lyrics, would be hard to distinguish from a multitude of songs of this era.
As an innovator and prime mover in the creation of bebop, Monk's place in the story of modern music is assured. But he clearly also had a strong melodic gift which he perhaps underplayed, and which as a result may have been slightly overlooked.

LOTS OF MONK INFO :

Thelonious Monk Website
Monk Institute of Jazz
God, One Note
AMG
P.Jeffrey's Monk Page
Round About Monk
Artists of Jazz
Laura Weeshoff Monk Page