Some call it, "really out of tune," some call it, "[delightfully] micro-tonal."

Stephen Altoft recently came to Iowa to do a masterclass and recital. He is a European trumpeter who is primarily interested in new (VERY NEW) works for the trumpet and also works which utilize atypical tunings. He brought with him a variety of instruments and told us of the history of their construction. His initial exploration with quarter tones dealt with alternate fingerings. I found it irresistable to later try to develop an ear for such pitches. It's odd but definitely interesting... He has a very extensive website: The Microtonal Trumpet