Question:  Leonard "Len" Benker Johnson organized a concert and a rally featuring an American bass singer who became involved with what?
Sentence (from "Len Johnson (boxer)"): Len Johnson was also a member of the Communist Party of Great Britain (joining the party in 1944 and later writing a boxing column for the party newspaper "The Daily Worker"), a trade unionist, a community leader in Moss Side, a local civil rights activist, and attended the 5th Pan-African Congress in Manchester.
Relevant evidence: No