The 77-year-old had been in remission for a few years before he died in the Royal Adelaide Hospital on April 16, the band announcement in a statement.

"Gavin entered our lives 60 years ago," band members Mick Bower, Brian Vaughton and Rick Morrison said.

"He joined our band as a bassist and from that moment became a member of our family; our brother.

"We will greatly miss our Gavin and treasure the life long bond we will share forever - from Mustangs to Masters.

"Our love eternally 'Spider'."

Mr Webb joined the trio who were then known as The Mustangs in 1965 after his brother placed an advert in an Adelaide newspaper for a student bass player wanting to practice with a group.

The band added lead singer Jim Keays the following year and took Australia by storm as The Masters Apprentices.

Mr Webb's basslines feature on seminal tracks including Undecided, Wars or Hands of Time, Buried and Dead, Hot Gully Wind, Elevator Driver and 1967 national song of the year Living in A Child's Dream.

Mr Webb married Suzette Belle in 1968 and they had a son Benjamin later that year.

In April 1968 he left the band due to stomach ulcers and was replaced by Glenn Wheatley until the band split in 1972.

Mr Webb reunited with The Masters Apprentices in 1986 for 20^th anniversary tours and the band has been touring around Adelaide since reuniting for the 2016 Fringe Festival.

"Gavin leaves behind an incredible musical legacy which will live forever in Australia's music history," the band said.