Mensch started his career in music management at the age of 26, managing AC/DC. In 1982, he formed the management company Q Prime with Cliff Burnstein. Their first client was Def Leppard. Q Prime has managed the careers of a large number of multiplatinum acts; their roster includes Metallica and Red Hot Chili Peppers, Muse, Josh Groban, Snow Patrol and many others, including Jimmy Page. The Financial Times has called Q Prime "One of the most admired artist management companies".
Peter David Mensch was born in New York, the oldest of three children to Martin, an attorney, and Jean Mensch, an educator. His family is Jewish. His sister, Barbara Sena Mensch, was the youngest hostage of the Dawson's Field hijackings of September 6, 1970. Peter graduated from Scardsdale High School in 1971. He attended Brandeis University and worked as a music director for the college radio station, which is where he met Cliff Burnstein. After graduating from Brandeis, he received his Masters Degree in Marketing from the University of Chicago.
Mensch began his professional career after graduating from the University of Chicago. His first assignment was as a label manager with Blank Records in New York. Shortly thereafter, he joined mega-talent firm, Leber-Krebs, as a tour accountant. He worked with such acts as Aerosmith and the Scorpions. As a tour accountant with Aerosmith Mensch came upon the Australian rock band AC/DC, and persuaded them to swap their previous manager, Michael Browning, for Leber Krebs. Mensch was assigned to manage the band as his first client; he was 26 years old.
On the advice of his friend Cliff Burnstein, then at Mercury Records, Mensch targeted the British group Def Leppard. He deliberately booked the band as support act on an AC/DC tour. A BBC documentary on the band records their unhappiness with their early managers Pete Martin and Frank Stuart-Brown, following a fist-fight between singer Joe Elliott and Martin. The film quotes Mensch as saying Burnstein told him "I don't care if they have managers...steal them from another set of managers." The band's drummer Rick Allen recollects that he did approach Mensch, and Mensch signed them to Leber Krebs. After a disagreement with Leber-Krebs over royalties, Mensch was terminated from that firm and started Q Prime with Cliff Burnstein. Def Leppard was the sole client to come with the new firm.
Q Prime management made their name in heavy metal music, managing, at various times, AC/DC, the Scorpions, Def Leppard, Dokken, Tesla, Suicidal Tendencies, Queensrÿche, and Metallica. In the early nineties their roster expanded to include alternative rock bands such as the Smashing Pumpkins, Hole, and Veruca Salt. They co-managed Madonna for one album, "Ray of Light," and also consulted for the Rolling Stones on their "Steel Wheels" tour in 1990. They also managed Shania Twain for part of her career. The firm's present roster includes Metallica, the Red Hot Chili Peppers, Muse, Snow Patrol, Foals, Silversun Pickups, Cage the Elephant, Dawes and others. They additionally manage country acts from their Q Prime Nashville imprint, including Eric Church and Gillian Welch, and the Black Keys. They managed the opera singer Renee Fleming for her crossover record "Dark Hope." As solo artists the firm manages Jimmy Page and Josh Groban.
In June 2011, he married his third wife, Louise Mensch, with whom he had been having an extramarital affair for 20 years. He has three children by his second wife, Melissa Meyer, whom he divorced in 2010. The divorce was contentious.
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