This paper discusses aspects of composing for a specific type of Balinese gamelan ensemble known as gendér wayang, a quartet of metallophones that accompanies shadow puppet plays and life-cycle rituals. The author is a composer and ethnomusicologist who spent many years studying this tradition and has conducted research on traditional compositional methods for the ensemble. He also teaches and leads a gendér wayang ensemble in London. The instrument's technical difficulty and the highly complex, rhythmically ambiguous nature of the traditional repertoire make this a particularly challenging ensemble to compose for. The paper explores connections between certain ritual pieces in the traditional repertoire, legends surrounding these pieces, and the author's own composition "The Birth of Kala" which formed part of a collaborative project with actor, storyteller and movement artist Tim Jones in 2012. The starting point of the concert was the instrument itself, with the music and storytelling a kind of meditation on it. The concert had three interwoven strands: firstly Balinese stories surrounding the origins of gendér including the birth of the demonic Kala, secondly traditional pieces, and thirdly the newly composed music. The latter took up most of the second half of the concert as a kind of abstraction of issues raised in the more narrative first half. This article presents a description and analysis together with score in cipher notation and references to the online video of the first performance. It then discusses some issues arising from the work, and from the analysis of it, locating the whole within the context of new gamelan composition.