Avrin, that's an intriguing claim. I don't quite buy it. Do you have some references to back this up? I'm not trying to corner you. It could be true, but as I think about it, there are other forms of music, especially the two you just quoted (jazz and trance) which have plenty of harmony. I haven't done any research on this. I know something about both computer science and music, but am not an expert in data compression algorithms. Here we're speaking of traditional non-lossy data compression optimized for music. There are arguably more "complex" or "interesting" chords or harmonies in classical music, as a generalization, although even that claim would bring strong criticism from jazz fans. Electronic or "trance" music, being generated by a computer, is going to be the most precisely in tune, mathematically, and have the most regular beat, as well. And the most repetition of sounds. Often no vocals. All those things lead to more compression. It also does have harmonies. They may be simple in nature, but even that would seem to argue for MORE compression, not less. I picture an orchestra. 100 instruments playing very well in tune, but each performer contributing their own tone and very slight variation in pitch, especially on orchestral string instruments which are all fretless. The result is a powerful artistic sound appealing to the human ear, but seems like murder on a compression algorithm, to me. There are beautiful harmonies which are not "mathematically in tune" in an absolute way, (e.g. 440 Hz) but sound fantastic, where all notes in the chord are in tune *relative to each other* like is emphasized in a barbershop quartet, but is also present in chamber music and lots of high-quality classical music. This also would seem bad for compression, to me. Plus it's present in the best jazz, as well. Non-existent in electronic music. Here's my theory. I think what you're observing, with classical music compressing better losslessly, has far more to do with the lack of very high frequencies. The typical orchestral performance has an occasional cymbal crash, but nothing like the constant high-hat or cymbals which are pervasive in both trance and jazz. There's no drum set in an orchestra. Even the high register of a violin can't compare (in Hz) to the airy "hissy" KHz of whispy electronic sounds and percussion beating regularly throughout the music. Mac Rhythm Guy
