Herbie Kalin, who has died aged 72 of a heart attack, and his brother Hal, were the Kalin Twins, promoted by Decca as two Elvis Presleys for the price of one and whose maddeningly catchy When was an international million-seller in 1958.
The song was regarded initially as a doubtful starter, having been rejected by the Everly Brothers. The Twins' producer, Jack Pleis, wasn't keen either, but his stop-start arrangement, punctuated by finger-clicks, assisted its climb into the American top 10, and then to number one in Britain.
After a London Palladium appearance and slots on BBC television's first pop show, Six-Five Special, the Twins undertook a British tour - as one of the first US rock'n'roll acts to do so - supported by Cliff Richard, who became a lifelong friend. Among later Kalin Twins recordings was a medley with Cliff, issued in 1989 when Herbie and Hal were special guests on his networked television spectacular from Wembley arena.
A succession of smaller hits followed When, but by 1960 Herbie and Hal were no longer serious chart contenders.
Born in Port Jervis, New York, they had been performing in public, together and apart, virtually from infancy, and they became professional musicians on leaving the local high school in 1952. Following Herbie's spell as a solo vocalist and Hal's US air force national service, the twins teamed up and played New York nightclubs - where, in 1957, they came to the attention of songwriter Clint Ballard Jr, who offered his services as manager. A debut single, Jumpin' Jack, flopped, but then came When.
Latterday releases included a US-only cover of Joe Brown's hit A Picture of You, a revival of the Everly Brothers' All I Have to do is Dream, 1979's patriotic American Eagle - and a 1980 disco re-make of When. By then, disc sales had long been adjuncts to earnings on the road, sometimes with Jack, a younger sibling, as the Kalin Brothers.
With their Remember When revue, the now bow-tied, tuxedoed and bearded Kalin Twins, from their base in Waldorf, Maryland, remained a cabaret draw until Hal's death (obituary, September 27 2005) in a road accident last August.
· He is survived by two sons and two daughters from his first marriage. His second wife Charlotte predeceased him. Herbie (Herbert Harry) Kalin, singer, born February 16 1934; died July 22 2006