Michael De Costa was a Principal Baritone for English National Opera and also worked with many other major opera companies throughout Britain. He was also a regular soloist in opera galas at the Royal Albert Hall and Royal Festival Hall. He was a soloist in Carl Orff's Carmina Burana in Bahrain, where he was privileged to meet several members of the Bahraini Royal Family. Michael also travelled to Ukraine to perform for Odessa State Opera and give masterclasses at Odessa State Conservatoire.

Since stepping down from full-time performing, Michael focused on the development of his teaching career at the highly successful De Costa Academy of Singing in York, which he established in 1988 to develop the 'bel canto' school of vocal production in the north of England.

Michael was the expert in voice production for the development of the electrolaryngoscope, a pioneering device developed by Professor David M. Howard at the University of York. The technology provides a real-time electronic display to show characteristics of the singing voice, in order to give visual feedback for use in professional vocal development. As part of the research, pupils at the Academy were analysed as part of the initial pilot studies.