What is the last name of the person who gave up the conductorship of the Purcell Singers in 1967?  Answer the above question based on the context below:  Holst had formed the Purcell Singers, a small semi-professional choir, in October 1952, largely at the instigation of Pears. From 1954 the choir became regular performers at the Aldeburgh Festival, with programmes ranging from rarely heard medieval music to 20th-century works. Among choir members who later achieved individual distinction were the bass-baritone John Shirley-Quirk, the tenors Robert Tear and Philip Langridge, and the founder and conductor of the Heinrich Schütz Choir, Roger Norrington. Langridge remembered with particular pleasure a performance in Orford church of Thomas Tallis's forty-part motet Spem in alium, on 2 July 1963.   When she gave up the conductorship of the choir in 1967, much of its musical mission, in particular its commitment to early music, was assumed by other groups, such as Norrington's Schütz Choir and the Purcell Consort formed by the ex-Purcell Singers chorister Grayston Burgess.On 2 June 1967 Holst shared the podium with Britten in the concert inaugurating the Aldeburgh Festival's new home at the Snape Maltings. From 1972 Holst was involved with the development of educational classes at the Maltings, which began with weekend singing classes and developed into the Britten-Pears School for Advanced Musical Studies, with its own training orchestra. By this time Imogen's performances at the festival had become increasingly rare, but in 1975 she conducted a concert of Gustav Holst's brass band music, held outdoors at Framlingham Castle. A report of the event described an evening of "persistent drizzle ... until a diminutive figure in a special scarlet dress took the conductor's baton. The band was transformed, and played Holst's Suite as it has never been played before".Britten had been in poor health since undergoing heart surgery in 1973, and on 4 December 1976 he died. Holst was unsure that she could maintain a working relationship with Pears alone, and on reaching the age of 70 in 1977, decided she would retire as artistic director after that year's festival. She made her...
A:
Holst