In some styles of Javanese wayang kulit, grimingan flows forth from the hands of the gender player for nearly four of the eight or so hours that comprise an all-night performance. Although their performances are regularly punctuated by other musical events, sometimes a gender player will be asked to perform grimingan for 30-40 minutes without pause. How does a musician generate such an extended solo performance? It turns out that the answer depends on whom you ask. Some performers say that you can play anything as long as it is in the correct mode or pathet. Other gender players tell you that they just keep repeating ‘the melody.’ Through interviews and recording sessions, it gradually became clear to me that each performer did possess a collection of melodies designated for use in the creation of grimingan segments. Working outward from transcriptions of different performers’ grimingan melodies in what they described as their most compact form, and by transcribing more than 50 hours of performance, I have documented the process by which performers expand their versions of compact melodies to fill the necessary minutes of accompaniment. While their approaches to the process are necessarily idiosyncratic, a few rules can be derived to describe the process in each mode. Transcription and analysis have revealed the process by which the performers created their music. Understanding the process revealed the flexible but identifiable nature of the form of grimingan.