Mark P. Wirtz born (September 3, 1943, Strasbourg, France) is an Alsatian pop music record producer, composer, singer, musician, author, and comedian. As a producer, Wirtz's most famous output is from the mid to late 1960s, when he worked at Abbey Road Studios with Beatles engineer Geoff Emerick, under contract to EMI. Wirtz is chiefly known for the never-completed A Teenage Opera concept album. Another track by Wirtz, "A Touch of Velvet, A Sting of Brass" under the name Mood Mosaic, became well known in Germany as the theme tune for Der Musikladen and was used by some radio stations and DJs in the UK as ident, notably Dave Lee Travis on Radio Caroline.
His signature style has been described by Mojo magazine as "Phil Spector scoring Camberwick Green", a sound most perfectly encapsulated on Wirtz's masterpiece, "Grocer Jack (Excerpt from A Teenage Opera)". This 1967 hit single is a densely orchestrated psychedelic marvel, which tells the whimsical and sad tale of an old man ("Grocer Jack"), who dies unappreciated, except by the children who loved him and miss him.