On 12 August 1909 Adolf and Fritz presented a farewell musical evening at the Beckerath house in Pyrmont. Next morning Fritz was off to the rigours of a Latvian winter and Adolf was thrown into a panic: they had never before suffered a serious parting and he realised for the first time how much their careers would separate them. He still made sure he sent Frieda one of his compositions for her eighteenth birthday that day, a setting in A major of Gottfried Keller's poem Abendlied: there would be a similar present every year up to her 55th birthday, nine days before her death. Since the spring they had forged an understanding that they would marry as soon as Adolf's future was settled; but naturally the Grüters family were worried about an engagement between two teenagers, neither of whom had experienced a relationship with anyone else. Within a week of her birthday, Frieda's father was trying unsuccessfully to talk her out of committing herself to Adolf so early; and brother Otto told her point-blank that the first love of an eighteen-year-old lad was hardly likely to be his last. All such remonstrations were in vain and only a few days later Otto was noting in his diary: ‘Adolf and Frieda much together’. Later that year, the Grüters parents even forbade the pair to communicate directly, which increased Adolf's feeling of isolation. But love soon found a way to circumvent the ban – Frieda's best friend in Bonn, Hanna Zorn, became a willing conduit for letters and messages. There was no doubting Adolf's devotion: Hanna testified that one evening in the winter of 1910–11, when Frieda was staying with the Zorns to prepare for her exams away from the musical uproar of the Grüters home, Adolf stood outside in the deep snow with his violin, serenading his beloved. By then it was tacitly accepted that they would wed as soon as he had embarked on his career.

Through Eldering, Busch had come to know Brahms’ friend Dr Gustav Ophüls, a redoubtable pianist from whom he gleaned much information about the way Brahms liked his works to be played.