Simon is a sought-after mastering engineer and has worked with a diverse range of clients in his long career at Abbey Road, ranging from pop to classical. He has mastered both stereo and 5.1 surround projects and was involved with many live music albums over the years. He is one of the world's leading audio restoration and remastering engineers, specialising in the use of CEDAR Audio’s software to enhance older recordings. He was responsible for all of the audio restoration on the Grammy Award-winning The Beatles album remasters (2009).

Coming from a classical music background, he uses his natural musical abilities to work in any genre, from rock and pop to symphonic orchestral soundtracks and from contemporary jazz to vocal and choral albums. Translating an artist’s wishes into musical reality always takes a wide variety of skills and Simon believes passionately in going the extra mile to give the client exactly what they want, using his wealth of knowledge and musical experience to produce great-sounding masters.

Simon has been nominated for a Grammy Award on multiple occasions and has mastered the work of some of the world's best-known names in pop, rock and classical music, including The Beatles, Paul McCartney (Under the Staircase – for Spotify), Depeche Mode (Live in Berlin), Wings (Rockshow), Sigur Ros (Heima) and numerous albums for the Choir of King's College, Cambridge.

Simon is also in demand for the soundtrack albums to many Hollywood blockbusters, having worked on Skyfall, Spectre, All the Money in the World, The Hobbit (Parts 2 and 3), Into the Woods, Les Misérables, The King's Speech and the 5.1 audio versions for Harry Potter and the Deathly Hallows (Parts 1 and 2). Since working on Howard Shore's scores to The Hobbit, Simon has mastered the complete back catalogue of Shore's film scores, including Naked Lunch, Maps to the Stars and Spotlight. TV soundtracks have included Our Planet for Netflix and Dr. Who (Series 11 - 13), as well as the video game music for Marvel: Guardians of the Galaxy by Richard Jacques.

In recent years, many London musical cast recordings have been mastered by ‘show-tune’ Simon, including Mary Poppins, Cabaret, Les Misérables, Miss Saigon, Sunset Boulevard and Oliver!

Other remastering projects have included Wings' Band on the Run and Ram albums (both Grammy nominated, with Band on the Run winning the Historical category in 2012). In 2017, Simon worked on the 50th anniversary reissue of Sgt. Pepper's Lonely Hearts Club Band and was involved in all The Beatles archive projects produced at Abbey Road. In 2020 Simon was again nominated for a Grammy in the Historical category for Bobbie Gentry: The Girl from Chickasaw County – The Complete Capitol Masters.

Simon won a Gramophone Award in 2007 for the CD remastering of the complete Lyrita catalogue of music by British composers. He was part of the Abbey Road team who remastered the complete studio recordings of Maria Callas, released in 2014 to great acclaim. For EMI and Warner, he remastered and restored countless archive tapes from the LP era, both classical and pop.

Outside mastering, Simon plays and teaches the organ, often accompanying local choirs.