This dissertation investigates the compositional style of Mátyás Seiber’s twelve-tone music through an analysis of three works composed between 1934 and 1960: String Quartet No. 2, Concert Piece for Violin and Piano, and Sonata for Violin and Piano. Chapter 1 provides an overview of the composer’s life and his compositional style. Chapter 2, on String Quartet No. 2 (1934-5), examines the subdivisions of the twelve-tone series into smaller pitch-class sets and introduces the concept of families. Chapter 3, on Concert Piece for Violin and Piano (1953-4), demonstrates the permutation of and within tetrachords derived from the prime series and the use of families as “harmonic” areas in the conventional sense. Chapter 4, on Sonata for Violin and Piano (1960), analyzes the prime series according to certain patterns that develop from the combination of ordered positions. This chapter also shows how families, which represent “harmonic” areas, are used for modulation in the classical sense.