What English composer/musician, known as the "Fifth Beatle," produced two records by British vocal group, The Master Singers?  
The Master Singers: The Master Singers were a British vocal group in the 1960s. The Master Singers:  Two of their records, "Highway Code" and "Weather Forecast", both produced by George Martin, reached the UK singles chart in 1966. George Martin: Sir George Henry Martin {'1': ", '2': ", '3': ", '4': "} (3 January 19268 March 2016) was an English record producer, arranger, composer, conductor, audio engineer, and musician. George Martin:  He was referred to as the "Fifth Beatle", including by Paul McCartney, in reference to his extensive involvement on each of the Beatles' original albums.
George Martin