Born in Budapest, Láng studied composition there from 1950 to 1958 at the Franz Liszt Academy of Music, first with János Viski and later with Ferenc Szabó (Boronkay and Willson 2001). After graduating, he worked as a freelance composer until 1966 ([Láng] 2003). From 1966 to 1984 he was Musical Adviser to the State Puppet Theatre, and in 1973 he joined the staff of the chamber music branch of the Liszt Academy. He also held guest lectureships at the University of Colorado in 1973, CNM in Mexico City in 1987, and the University of New Mexico in 1988 (Boronkay and Willson 2001). He served as Secretary General of the Association of Hungarian Musicians from 1978–90, was a member of the Executive Committees of the International Society for Contemporary Music and the International Music Council (UNESCO) in 1984–87 and 1989–93, respectively ([Láng] 2003).
He has twice been awarded the Erkel Prize (in 1968 and 1975), was made Artist of Merit in 1985, and has won the Bartók-Pásztori Prize in 1994 (Boronkay and Willson 2001).
In his early mature works, Láng adopted the serial techniques that had become fashionable in the early 1960s, showing the influence of Boulez and Schoenberg, but still managing a clever and effective synthesis of these styles with traditional Hungarian elements derived from Bartók in all areas: melody, harmony, rhythm, and texture—a synthesis perhaps best demonstrated in his Variations and Allegro (1965), which is an arrangement of an earlier symphony (Walsh 1969, 43). His music from this period is marked by an absorption with the theatre, even in chamber and solo instrumental works, such as Monodia for clarinet, which is intended for stage or concert performance (Boronkay and Willson 2001). Other important works from the sixties are the first two Wind Quintets (1963 and 1966), a ballet on Thomas Mann's Mario and the Magician (1962), and a Chamber Cantata to words by Attila József (1962) (Walsh 1969, 43). Another feature of Láng’s style is the use of cyclic form, and his later music tends to consist of sequences of short movements constructed from small motifs, which he calls "micro-organisms". These traits are found, for example, in his Second Wind Quintet of 1966 and Third String Quartet of 1978 (Boronkay and Willson 2001). The movements in such works are often linked by improvisatory solo interludes, as in the Second String Quartet of 1966 (Kárpáti 1969, 9).
Although Láng also worked briefly with electronic music as early as 1974 (Surface Metamorphoses), he turned seriously to this medium beginning only in the late 1990s, for example Esteledés (Nightfall, 1997), which uses live electronics to manipulate sounds of a trumpet and Korean bell (Boronkay and Willson 2001). More recent works with electronics are the Capriccio metronomico for tape (2001), and the Third Chamber Cantata, "No Man Is an Island", to words of John Donne (2001), for soprano, five instruments, and tape (Halász 2003, 1155).
- Boronkay, Antal, and Rachel Beckles Willson. 2001. "Láng, István". The New Grove Dictionary of Music and Musicians, second edition, edited by Stanley Sadie and John Tyrrell. London: Macmillan Publishers.
- Halász, Péter. 2003. "Láng, István". Die Musik in Geschichte und Gegenwart: allgemeine Enzyklopädie der Musik, second, revised edition, edited by Ludwig Finscher. Personenteil 10: Kem-Ler, 1154–55. Kassel & New York: Bärenreiter; Stuttgart: Metzler, ISBN 978-3-7618-1120-7 (Bärenreiter); ISBN 978-3-476-41019-1 (Metzler).
- Hollós, Máté. 2003. "'Nem vagyok elég öreg ahhoz, hogy ne újítsak'" ["I am not old enough not to innovate"]. Muzsika 46, no. 4 (April): 3–4.
- Kárpáti, János. 1969. "Some Trends among Younger Composers", Tempo, new series, no. 88 (Spring): 5–10.
- Kárpáti, János. 1975. "Láng István. II: Kamarazene" [Láng II: chamber music], Muzsika 18, no. 11 (November): 34–36.
- [Láng, István]. 2003. "Láng, István", International Who's Who in Classical Music 2003, 19th edition, edited by David Michael Cummings, 446. London and New York:Europa Publications. ISBN 1-85743-174-X.
- Walsh, Stephen. 1969. "An Outsider's View". Tempo, new series, no. 88 (Spring): 38–47.