Students at the Royal Academy of Music in London, the Englishwoman Ethel Bartlett (1896-1978) and the Scotsman Rae Robertson (1893-1956) met at the end of the First World War. Their collaboration as a duo took shape three years later with a series of concerts at the Wigmore Hall that launched their careers, but individually Ethel had been the exclusive pianist of cellist John Barbirolli (the future conductor) and Rae the accompanist of singers.

Enrolled in the British army, wounded twice in the arm and hand on the Somme front and at Ypres, he resumed his musical studies after the armistice and married Ethel in 1921. Very quickly, the duet made a name for itself on the British scene and made the public rediscover the genre of the piano duet, which had fallen into disuse in the United Kingdom.

In the absence of a consistent repertoire, the two musicians visited libraries, commissioned works from well-known composers and Rae made transcriptions or wrote scores such as the Elizabethan Suite. The duo continued to add to the body of work for two pianos with Bax's Sonata, Berkeley's Polka Op. 5 performed in 1934 for Eleanor Roosevelt, Britten's Introduction and Rondo alla Burlesca, Scottish Ballad Op. 26 and Mazurka Elegiaca Op. 23 No. 2 and Martinu's Three Czech Dances.

Listening to the recordings made by the two artists - in particular the reissue of an anthology of some of their performances between 1927 and 1947 (with APR in 2013) - one is struck by their fusional and natural understanding beyond a simple artistic companionship, whether in the transcriptions of J-S. Bach's transcriptions, Liszt's Liebesträume No. 3 or Debussy's En blanc et noir. Indeed, for them, the communion of thought exceeds the purely technical realization.

Celebrated in North America, Europe but also in South America and southern Africa, the duo performs an average of more than a hundred times a year in recital or in concert (for example in July 1940, exceeding the required capacity, the Hollywood Bowl welcomes them in front of 35,000 listeners).

When Rae died in 1956, Ethel continued to teach in California and died in Los Angeles, the couple's adopted home, twenty-two years later. After a concert in Montreal, a Canadian critic raved about their complicity: "Bartlett & Robertson's playing is unique. One thinks of them not as two people with two pianos, but as four hands at once, a double keyboard controlled by a single mind."