Ludwig Van Beethoven (1770–1827), German composer. String Quartet in F Major, Opus 135, epigraph to 4th movement (1826).
The movement was entitled, Der schwer gefasste Entschluss, or "The Decision Taken with Difficulty." "Es muss sein" was one of Beethoven's favorite phrases. (Quoted in The Letters of Beethoven, vol. 3, no. 1318, ed. Emily Anderson, 1961.).