This crisis in his life – when he cut himself off from the landscape that had formed him and the tradition that was his main source of cultural nourishment – is perhaps the best point at which to consider Adolf Busch the man, through the perceptions of relations and friends. Like his brother Fritz, he was deceptively tall, a little under six foot (1.79 metres): his heavy build in adulthood made him appear stockier and his skiing accident left him with one leg slightly shorter than the other and an almost imperceptible limp. ‘He had a peasant figure – he wasn't slim and he wasn't fat’, his niece Hildegart Nicholas said. As Evelyn Rothwell saw him, ‘He was like a large, benign bear, slightly shaggy, always with his hair falling over his face – a round, highly coloured face and bright, piercing blue eyes. He was always warm, outgoing, interested, eager – almost like a child’. This view was echoed by Dea Gombrich: ‘It was almost a child's face’. Meeting him with his son-in-law in 1939, a journalist reported that ‘his unlined, pink face and athletic figure make him look almost as young as the slight, boyish Serkin’. In Toni Booth's eyes ‘He was tall, with very broad shoulders, and looked as if he liked running’. And Amalie Serkin saw him as ‘not at all clumsy in appearance but stately, though never pompous – just a tall, big, blond man’. As a boy he had fair hair but it had darkened to reddish-brown by his early twenties – although in his fifties he still struck the young Eugene Istomin as ‘a great blond giant’. In the late 1920s and early 1930s he sported such a short crewcut that on his second visit to America he was described as ‘bristly haired’. Robert Dressler, Busch's pupil in his last years, said: ‘To me he always looked perfectly healthy, hale and hearty. He had very red cheeks, which is typical of a certain type of mostly southern German’. Conte Enrico di San Martino, president of the Accademia di Santa Cecilia, wrote:

Adolf Busch was a towering figure in the musical life of the twentieth century. He was also one of the great individuals of his time, a man of unquenchable idealism, integrity and intellectual rigour who lived out his beliefs and often suffered for them. Now that we can see the twentieth century entire, it is difficult to think of a more important German musician than Busch (except, perhaps, Hindemith) from that era. As man and artist he put most of his contemporaries in the shade and his life was an expression of almost heroic honesty and simplicity.

Yet he is not as well known today as he should be. His career as violinist and composer, like those of so many central Europeans, was disrupted by two catastrophic wars; and his decision to boycott his native country in 1933, when he could easily have stayed and prospered as others did, further fractured his life. This one action made him an exile, cost him the precious cultural nourishment of his native land and deprived him of his most devoted audience, virtually ending his prospects as a composer. Five years later he renounced all his concerts in Italy, where he was hugely popular, in protest at Mussolini's anti-Semitic laws. In America, where he settled at the end of 1939, his kind of musicality – which placed vigour and expression above virtuosity – was not fully appreciated. Any one of these setbacks could have spelt death to such a sensitive artist; and yet he rose above even the mental devastation which went with being a German, in the knowledge of what his people were doing during the Hitler decade.

In one biography of Wilhelm Furtwängler, it is implied that the Busch brothers found it easy to leave Germany in 1933. In another, they are listed as ‘expelled artists’. In a study of Furtwängler's recordings, it is stated that in forsaking their native country they ‘did so not because they were better men than Furtwängler, or had greater foresight, but because they had different priorities’.

While the rest of Europe went to war, life continued relatively normally for the Busches and Serkins in neutral Switzerland, although it seemed far from certain that Hitler would respect that neutrality and refrain from invading. Frieda, chafing at the compromises she felt the Swiss were making with their Nazi neighbours, fired off a letter to Werner Reinhart in which she complained about the engagement of Furtwängler to conduct in Winterthur and the willingness of the Winterthur City Orchestra to continue giving concerts in Konstanz, on the German side of the border – and incidentally chided Reinhart for not supporting the Lucerne Festival. After an interval Reinhart wrote a seven-page rejoinder, setting out the Swiss policy of neutrality in music, as in other things, and questioning the validity of excluding artists such as Walter Gieseking from the Lucerne event on purely political grounds. Much of September was spent by the Busch party at the little village of Eriz near Thun, where the reality of the international situation could be held at bay for a few weeks. Joseph Segal, who stayed with his mother in the same small three-storey house as the Serkins, found that he was expected to have his violin lessons upstairs, while Serkin practised thunderously downstairs. ‘Play forte!’ was the riposte from Busch, who rode up the hill on a bicycle from his own holiday home for the lessons. ‘He would come in, panting very hard – he was quite a heavy man – and take his working violin straight out of its case’, Segal remembered. ‘He would play with me a bit here and there.’

This talented pupil, born in Haifa of Russian parents, came with the recommendation of Sir Adrian Boult, who rehearsed the Beethoven Concerto with Segal and the BBC Symphony Orchestra as part of the first prize that the then fourteen-year-old won in the 1938 British Empire Violin Competition. Busch relented in his opposition to teaching prodigies because he was so taken with Segal's father Levi – who was still based in Palestine most of the time, while Joseph was accompanied abroad by his equally pleasant mother, Yaffa.