Were it not for Billboard's temporary decision to discontinue its R&B chart, 1964's "Mercy Mercy" would unequivocally rank among the biggest of Don Covay's scant few hits. As it stands, the song is one of only two Covay singles to make the pop Top 40 (the other was "I Was Checkin' Out She Was Checkin' In"), but there's no real way to measure its commercial impact among black audiences. Suffice to say, "Mercy Mercy" was a major seller in the R&B market, and has major significance for rock fans as well. The chiming, subtly sophisticated guitar work that overlays the song's choppy groove belongs to none other than a young Jimi Hendrix, in one of his early session-musician appearances. But the most immediately striking thing about the track is Covay's vocal, which even on first listen will cause most any rock fan to sit up and wonder why he sounds so uncannily like Mick Jagger -- in his phrasing and inflection as well as his attitude. In point of fact, it's the other way around -- when the Rolling Stones covered "Mercy Mercy" on their 1965 LP Out of Our Heads, Jagger clearly modeled his vocal on Covay's original, which apparently had a lasting impact on the way Jagger subsequently used his voice. For his part, Covay -- generally more noted as a songwriter than a singer -- turns in one of his most assured vocal performances, sounding a little too brash to really need much mercy. Originally cut for the small independent Rosemart label, "Mercy Mercy" was picked up for wider distribution by Atlantic, and reached number 35 on the pop charts.