And the 29-year-old star recalled how his dad introduced him to classic records from a young age.
He said: “After work, he would come home, crack open a bottle of red and play me all these fantastic records from Elton John to Pink Floyd.
“I begged him for a guitar, so he brought me a second-hand one and a chord book.
“He said: ‘There we go, there’s a thousand chords, so start there.’ I kinda panicked.”
Callum was just 10 when he played his first gigs.
He recalled: “I started playing pubs when I was around 10. My dad would put a wee ashtray on the floor and ask me to sing Elvis and people would chuck money in it.
“I used to play the roughest bars imaginable. In one – I won’t tell you which because they’re good people and I don’t want to dob them in – a prostitute used to come and sit right in front of me. And she would spread her legs whenever I played The Beatles.
“I was quite a young lad, so I thought, ‘Woah, okay’. You never knew what you were going to get there.” Meanwhile, the ‘Tears in My Eyes’ singer’s tour in support of his album, ‘People Like Us’, has been postponed three times due to the coronavirus pandemic, which he’s found “really difficult”.
He said: “Performing is my medicine, my release, so to not have that is really difficult.
“It took me two years to produce this album, and now I won’t be able to perform it for another two.
“I know we’re making these sacrifices for family and friends, so that helps me keep on.”