From his earliest years, Callum has the ability to improvise and harmonise. At the age of two, he is picking out melodies on the piano, and begins lessons at five. Aged nine, he takes an interest in jazz, which becomes his main enthusiasm for many years.
Forms first band (a skiffle group) playing banjo, while still in primary school, then a jazz band (playing piano) in secondary school.
At eighteen, joins Fergie MacDonald's Highland Dance Band as pianist, playing Scottish traditional music for dancing. This leads to his first experience of recording, making three LP albums and an EP with the band, and a first experience of broadcasting on BBC programmes.
A year and a half later, he is invited to join George Penman's Jazzmen playing trumpet, and works with the band for periods over the next twelve years, sometimes playing piano or tuba.
In 1972, a guitarist friend encourages him to become involved in writing pop songs. With two other writers, the group Hope Street is formed and a publishing contract obtained with Chappell Music. The group records singles for EMI. In 1974, Callum wins an international song competition in Malta, which encourages him to pursue song writing. He next collaborates with another Glasgow songwriter, Harry Barrie, this time under contract to EMI Publishing. In this period, he also records a programme of ragtime piano music for Radio Clyde.
From 1976, he leads a 4-piece band in a Glasgow nightspot playing keyboards. The group plays for dancing and backs cabaret acts.
In 1978, the band is booked onto the Cunard cruise liner QE2 and subsequently on the Cunard Countess in the Caribbean.
After a summer season in the Channel Islands in 1979, Callum moves to London to work with independent producer/publisher, Larry Page, staying in the capital for almost five years. Apart from writing songs for various singers, he also begins to write instrumental pieces. He records an album of his own compositions under the pseudonym of Michael Park and his Orchestra, also having pieces recorded by the Johnny Pearson and Larry Page orchestras. Another typical project involves writing English lyrics for an album of twelve European hit songs, each from a different country. He plays solo piano around the famous West End hotels, and plays on recording sessions.
Leaving London in 1984, he works abroad in piano bars in Norway and five-star hotels in Switzerland and Monte Carlo, before returning to Scotland.
While resident pianist at the Edinburgh Sheraton Hotel, he completes a three-year college course in piano tuning and maintenance, going into business for four years before returning to full-time piano playing.
During the 1990s, composition becomes a more serious activity and a Piano Concerto is composed in 1995. This Concerto is first performed and recorded by the eminent Scottish concert pianist Murray McLachlan, along with Callum's Rhapsody on Themes of Grieg. Solo piano music, chamber music for wind quintet, piano quintet, harp trio, saxophone quartet, string quartet, clarinet, and viola, plus song cycles for mezzo-soprano and baritone voices are all included in his output to date.
Working as solo pianist with P&O Cruises from 2000 to 2002, he draws on an accumulated repertoire of more than eleven hundred titles, mainly in his own improvised arrangements. He subsequently moves to Milan, Italy where he now lives with his partner Manuela, while continuing to compose concert music.