Fans have been paying tribute to the musician this morning after his "heartbroken" bandmates announced his death on social media.
Timmy had been battling skin cancer after he was diagnosed with stage three malignant melanoma in 2016 but the circumstances of his death are still unclear.
Members Mark Franks, Mike Crawshaw, Darren Everest and Lachie Chapman wrote on Twitter: "It is with the greatest sadness that we have to announce that our dear friend and brother Timmy has passed away.
"We know this news will be as heartbreaking for you all as it is for us.
"We appreciate your love and support at this difficult time."
Shocked fans have today been paying tribute to the singer.
One said: "Stunned and shocked to hear that Timmy Matley from @the_overtones has passed away. Had the pleasure of meeting him and the rest of the band back in 2012 when they played in Aberdeen. Rest in peace x"
Another added: "So sorry to hear of the passing of corkman Timmy Matley of @the_overtones! A gentleman and incredible talent. Sympathies to Timmy's family, friends and bandmates."
A third said: "So shocked and saddened to hear that Timmy Matley of The Overtones has passed away. I don’t believe in heaven but if there is a better place it’s gained the voice of another angel. It’s true what they say - only the good die young."
Timmy joined The Overtones, originally called DYYCE and Lexi Joe, in 2010.
They achieved four top-ten albums in the UK and their debut, Good Ol' Fashioned Love, reached number four in the charts.
In 2016 the group toured with stage show That's Entertainment and then A Christmas Tour later that year, but Timmy was forced to pull out after his skin cancer diagnosis.
But he had returned to performing with the group and had been looking forward to their summer tour in July, with their first gig at Barnstaple Queens Theatre.
He had been due to do a 15,000ft skydive to raise money for The Royal Marsden in London on May 3.
It was the hospital where he received his cancer treatment and he had raised more than £5,000 for them already.
Timmy was also due to perform at City Hall on June 12 for a charity concert to raise funds for Down's Syndrome.