There are multiple artists with this name:

1) John Sinclair (born October 2, 1941 in Flint, Michigan, United States) is a Detroit poet, one-time manager of the band MC5, and leader of the White Panther Party from November 1968 to July 1969. He was jailed in 1969 after giving two joints of marijuana to an undercover narcotics officer. His case received international attention when John Lennon performed at a benefit concert on his behalf in 1971.

John Sinclair has released several albums as leader of the Blues Scholars (named after Professor Longhair's band). The music typically features Sinclair's poetry recited over jazz and blues accompaniment. The band first came together in Detroit in 1982.

Sinclair moved to New Orleans in 1991 and assembled a new edition of the Blues Scholars. He also joined the staff of WWOZ radio, winning Offbeat Magazine's reader's poll as the city's most popular DJ five years in a row (1999-2003).

The Blues Scholars have on occasion been joined on stage and in the recording studio by former MC5 guitarist Wayne Kramer. Alive Records released the Blues Scholars recordings.

In 2004, John Sinclair moved to Amsterdam. He continues to tour and record with the Blues Scholars, and hosts a weekly radio show, The John Sinclair Show, which is streamed live and is also available as a podcast. He now lives in Detroit, MI.

http://www.JohnSinclair.us/

2) A german full cast audio drama. 107 Episodes where released by Tonstudio Braun from 1981 to 1991.
Since 2000 the label Lübbe-Audio produces and releases new Episodes with the subheading "Edition 2000".

3) An English folk singer recorded by Alan Lomax, his rendition of "The Grey Silkie" appeared on Lomax' 1961 album The Folk Songs of Britain
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