Bobby Hatfield of the Righteous Brothers has been found dead at a US hotel.
Hatfield, who was 63, partnered Bill Medley on hits like Unchained Melodyand You've Lost That Lovin'Feelin'".
His manager, David Cohen, said Hatfield's body was discovered half an hour before the duo were due to give a performance at the Michigan University campus.
Hatfield was found in bed. Cohen says the cause of death is unknown, adding: "It's a shock, a real shock." He said Medley, who teamed up with Hatfield 42 years ago, was "broken up. He's not even coherent".
The duo had been due to perform at the Miller Auditorium. Executive director Bill Biddle told the audience the show had been cancelled because of "a personal emergency of an unspecified nature".
The Righteous Brothers were inducted into the Rock 'n' Roll Hall of Fame earlier this year. Their signature 1964 single, You've Lost That Lovin' Feeling, has been cited by numerous sources as the most-programmed song in radio history.
Later 1960s hits included Soul and Inspirationand Unchained Melody. After splitting up in 1968, they reunited in 1974 and returned to the top of the charts with Rock 'n' Roll Heaven.