Holton built Ellis a custom trumpet which he received in September 1965. Its additional (fourth) valve enabled it to produce quarter tones. The inspiration for this may have been due to his studies of Indian music, which includes bent pitches that some ethnomusicologists refer to as "microtones". However, it was probably more the result of Ellis's involvement with avant-garde classical music in which many composers were experimenting with Western tonality and intervals, especially Harry Partch, with whom Ellis is known to have met and discussed ideas.