In 1927, he won a contest sponsored by the Baltimore Sun, playing a Beethoven minuet, and a year later he ran away from home to New York.

He broke the typecasting and appeared in a dinner jacket in the 1934 Paramount film Many Happy Returns, and was hired by theatrical producer C. B. Cochran to perform in London.

"[4] He became a star in the United Kingdom and the Empire, where, it has been written, harmonica sales increased 20-fold and 300,000 people joined fan clubs.

Other works he played in harmonica arrangements were by Bartók, Beethoven (Minuet in G), Debussy, Falla, Gershwin (Rhapsody in Blue), Mozart (slow movement from the Oboe Quartet, K. 470), Poulenc, Ravel (Boléro), Stravinsky and Walton.

After being blacklisted and an unsuccessful libel suit decided in 1950, he moved to the United Kingdom in 1951 and settled in London,[6][7] where he remained the rest of his life.

His other film scores included A Cry from the Streets (1958), The Hellions (1961), The Hook (1963), King & Country (1964) and A High Wind in Jamaica (1965).

The album included Peter Gabriel, Oleta Adams, Elton John, Sting, Jon Bon Jovi and Richie Sambora, Meat Loaf, Sinéad O'Connor, Robert Palmer, Cher, Kate Bush, Elvis Costello, Courtney Pine, Issy Van Randwyck, Lisa Stansfield and Carly Simon, all of whom sang Gershwin tunes with an orchestra and Adler adding harmonica solos.

Adler appeared in five movies, including Sidewalks of London (1938), in which he played a harmonica virtuoso named Constantine.

Adler wrote an autobiography entitled It Ain't Necessarily So in 1985, and was food critic for Harpers & Queen.

He appeared on the Jack Benny radio program[10] several times, entertaining disabled soldiers in the US during World War II.

Adler was a close friend of Peter Stringfellow, who hosted his birthday parties at his central London club for at least the last ten years of his life.