He is not a composer. He is shyster business man in the recording industry who cheated performers and lost money. From wikipedia:

After Venture Records Inc. folded, Avant remained in Los Angeles and founded Sussex Records on December 18, 1969. The company went out of business in June 1975, with the IRS seizing and auctioning off all assets because of $48,000 in federal tax liens... Sussex Records was mentioned in the documentary Searching for Sugar Man. Interviewees in the documentary said in their interviews that they paid royalties from sales of Sixto Rodriguez' records to Sussex Records. It is strongly implied in the documentary that Sixto Rodriguez had been cheated out of the royalties... Under Avant Garde Broadcasting, Inc....Management refused to accept all counsel or advice on how to run the station, despite never turning a profit. Ultimately, AVG was forced into bankruptcy by Urban National on November 20, 1975, when it defaulted on promissory notes and warrants of around $400,000. Avant lost about $611,168.67 in the bankruptcy