Peter Wallengren, the man behind Wallengren Music & Theatre Management, began his career in the music industry in 2001 when he was charged with developing "Amnesty in Concert" a part of Amnesty International. The concept was to lift Amnesty International's image among music lovers.

The function as production manager led to a position as leader of Søren Højberg Booking's office in Copenhagen, first as an agent and later primarily as promoter and producer.

In November 2006 Peter Wallengren left Søren Højbjerg Booking and established Wallengren Music & Production. Later, in 2009, he founded Wallengren Music & Theatre Management which works within three areas: production of tours, promotion of international acts and, to a lesser degree, take on tasks as agent for Danish artists.