Hatfield (left) and Bill Medley had global success

The song, recorded by famed producer Phil Spector, is said to be the most-played song in US radio history.

Hatfield was born in Beaver Dam in Wisconsin in August 1940. His family moved to Anaheim, California, when he was four.

He helped organise music groups at high school, while helping his parents who ran a dry-cleaning business.

'Righteous, brothers'

He had considered a career as a professional baseballer, but formed a band while attending Long Beach State University, where he would play at bars and prom dances.

In 1962 he formed a five-piece group called The Paramours, which included Bill Medley. Initially Medley handled the group's songwriting and production duties.

According to the Righteous Brothers website, the group changed their name after a 1963 concert where a crowd member yelled out "That was righteous, brothers!" during one of their performances.

Medley and Hatfield (right) split for six years

They renamed themselves before the release of their first album in 1963.

Their first hit came with the release of the song You've Lost That Lovin' Feelin', produced by the respected Phil Spector, and which he co-wrote with Barry Mann and Cynthia Weil. It was a US number one.

Running to four minutes, the song was considered to be at the limits of what could be played on US radio in the 1960s.

Its wall-of-sound style popularised the term "blue-eyed soul" - a term used to describe white soul at a time when the genre was dominated by black artists. Their second album was called Some Blue-Eyed Soul.

The duo had three further hits on Spector's Philles label in 1965 - Just Once in My Life, Ebb Tide and the epic ballad Unchained Melody, all characterised by booming production and bold vocal crescendos.

They had another US number one hit with (You're My) Soul and Inspiration in 1966.

The duo were inducted into the Rock and Roll Hall of Fame this year

Medley left the duo to begin a solo career in 1968, with Hatfield keeping the Righteous Brothers together with singer Jimmy Walker.

He and Medley reunited in 1974, and had another US number one with the track Rock and Roll Heaven, a tribute to dead rock stars including Janis Joplin, Otis Redding and Jim Morrison.

The returned to touring in the 1980s, and in 1990 Unchained Melody became a hit again on both sides of the Atlantic thanks to its inclusion in the film Ghost. It also won them a best pop performance by a duo or group with vocal in the 1991 Grammys.