Although his playing could command a free and piercing (yet musical) performance, Don Ellis' mark was made on the outstanding large ensembles he assembled in the 1970s. Multiple horns mixed with a large woodwind section and surreptitious strings over throbbing rhythms. Ellis' orchestra relied heavily on odd time signatures to drive their grooves, but their sound was always fresh and exciting, rather than forced. Ellis himself experimented with different sounds for his trumpet, inventing a four-valve instrument which could play quarter tones and using effects in a fashion similar to Miles Davis. He gained valuable experience and influence working with Charles Mingus, George Russell and Eric Dolphy; his music similarly managed to be innovative and unstructured at times, but never long enough to alienate a listener.