If there was one place that proved vital to Maconchy's development as a composer, it was the Royal College of Music (RCM). Shortly after moving to London and eventually settling in Paddington, Maconchy began her studies at the College in the Christmas term of 1923. Initially, her principal study was piano and she was assigned to Arthur Alexander (1891–1969) for lessons. For her second study, she elected to study composition and was assigned to Irish composer Charles Wood (1866–1926). Maconchy also enrolled in lessons in harmony and counterpoint with Charles Herbert Kitson (1874–1944). Life in London was a dramatic change from Ireland, and it took Maconchy some time to adjust, as she recalled: ‘I was a shy and unsophisticated schoolgirl … [s]o this plunge into the musical life of London was thrilling but also overwhelming, and it took me a year or two to surface’.

In the 1920s, the RCM was going through an adjustment of its own as it adapted to the dramatic increase of students after the war, as well as a whirlwind of change ushered in by Hugh Allen (1869–1946), who had been appointed Director of the College in 1919 after the death of Sir Hubert Parry in October 1918. While the most visible change to the College after the war was the abolition of sex-segregated staircases, Allen also made a number of alterations to the institution that included a complete reorganisation of the teaching staff, as well as reforms to its curriculum, and an expansion of performance opportunities for students. Guy Warrack (1900–86), who both studied and later taught at the RCM in the 1920s, aptly characterised the College's growth under Allen's leadership as ‘a period of vigorous and almost breathless creation, revival and expansion. There was any amount of music to be absorbed on every side.’ Contrary to the popular image of the College in the 1920s as an inherently conservative institution where, according to Elisabeth Lutyens (1906–83), ‘Brahms was the god of new music’, an examination of College concert programmes reveals that this period was in fact much more diverse, with a heavy influx of French and Russian repertoire as works by Debussy, Franck, Saint-Saëns, Ravel, Borodin, Rachmaninoff, and Tchaikovsky were routinely performed at the College, with even composers such as Stravinsky and Schönberg making appearances in programmes.