Peter Ernst Lassen was born in Copenhagen, where he also was educated as a pianist and conductor. He completed his studies in Salzburg, Berlin, Leningrad and Krakow.

He has held positions with symphony orchestras as well as in different theatres, Soenderjyllands Symphony Orchestra, The Danish Radio Sinfonietta, The Royal Theater, Copenhagen, Hamburgische Staatsoper and Deutsche Oper, Berlin.

As a guest conductor he has conducted in many of the major houses of Europe (Royal Opera, Covent Garden, Paris National Opera, Bayerische Staatsoper, Munich, Sächische Staatsoper, Dresden, Operan, Stockholm, Norwegian Opera, Oslo, Finnish National Opera, Helsinki, Deutsche Staatsoper, Berlin and Wiener Staatsoper, Vienna) and on tours in the Metropolitan Opera, New York, Kennedy Center, Washington, San Francisko Opera, Stuttgart, Wiesbaden, Wiener Staatsoper, Cairo Opera, Tokyo, Osaka, Kyoto, Beijing og Shanghai.