My knowledge of Erroll Garner's songwriting is limited to the fact that he composed one great song, "Misty", in 1954, later given lyrics by Johnny Burke - a song which was popularised in Clint Eastwood's 1971 movie thriller Play Misty For Me, but which first came to my attention when Ray Stevens released what might best be described as his "hillbilly" version in 1975. I realised even from Stevens' version that this was no ordinary pop song, but one with harmonic and melodic subtleties which hinted at the presence of a great musician.
I now know that Erroll Garner was not just a great musician, but one of the finest and most original jazz pianists of the 20th century - a man who played alongside the greats, including the legendary Charlie Parker.
As a jazz pianist I guess Erroll's prime interest was probably not in writing songs as such, and, although Burke and Sammy Cahn added lyrics to several other of his compositions, as far as I know "Misty" is the only Garner song that has achieved wide popular success. It has also become a standard of the jazz repertoire.