He studied piano with Jürgen Uhde and composition and theory with Johann Nepomuk David at the Musikhochschule Stuttgart from 1955 to 1958[2] and was the first private student of the Italian composer Luigi Nono in Venice from 1958 to 1960.

Lachenmann has referred to his compositions as musique concrète instrumentale, implying a musical language that embraces the entire sound-world made accessible through unconventional playing techniques.

His scores place enormous demands on performers, due to the plethora of techniques that he has invented for wind, brass and string instruments.

His more important works include his opera Das Mädchen mit den Schwefelhölzern [The Little Match Girl] (1990–96, after Hans Christian Andersen, Leonardo da Vinci and Gudrun Ensslin), the orchestral pieces Schwankungen am Rand (1974–75, for eight brass, two electric guitars, two pianos, four thunder sheets, and 34 strings), Accanto (1975–76, for clarinet, large orchestra and tape), and NUN (1997–99, for flute, trombone, male chorus, and large orchestra), the ensemble works Mouvement (- vor der Erstarrung) (1982–84, for three ad hoc players and 14 players), and "...zwei Gefühle...", Musik mit Leonardo (1992 [later incorporated in opera Das Mädchen mit den Schwefelhölzern], after Leonardo da Vinci, for two speakers and 22 players), and three string quartets (Gran Torso, 1971, revised 1976, 1988; Reigen seliger Geister, 1989; Grido, 2001), as well as other orchestral, ensemble and chamber works and six piano pieces.

He is also noted for his articles, essays and lectures, many of which appear in Musik als existentielle Erfahrung (Music as Existential Experience) (Breitkopf & Härtel, Wiesbaden, 1996).