Glenn started playing professionally at age 16 in a piano bar, subsequently playing with blues and jazz musicians including Sonny Rhodes, Johnny Copeland, and Richie Cole.

The two started talking about music, and after Dean told Glenn about Ween and Glenn talked about his experience as a keyboardist, Dean invited him to play a bit at his studio.

[1] In 2006, he resumed his membership in Blood, Sweat and Tears (while continuing with Ween).

He is also a vocalist and keyboardist for Scott Rednor and His Band and The Happy Dog.

[2] He has a son named Charles Glenn McClelland who is also a musician.