In a message dated 5/15/03 5:03:11 PM, Richard.Brekne@grieg.uib.no writes: >I believe the phenomena is called difference tones Supposedly Mozart was aware of this phenomenon and used it in his compositions to fill out the sound in certain circumstances. In college theory class we were exposed to difference tones, but high pitched sine tones were used. Odd intervals like a major second or a perfect fourth could produce a very audible lower tone a couple of octaves down. This note was predictable but I can't remember how they were determined. I do remember hearing a series of high pitched intervals that clearly resulted in a low C major scale. It was really entertaining. (For a theory class.) Think of that Emergency Broadcast System test tone on the radio ("THIS IS ONLY A TEST!! IF IT WERE A REAL EMERGENCY...). That used to be a major second, A4 and B4, and you could hear the difference tone if the TV was cranked loud enough. (I say 'used to be' because the last time I heard the Emergency Broadcast announcement, it was a modem tone.) I could imagine that a woodwind quintet might produce difference tones on certain chords that could be audible, but the idea of playing two piano notes to produce a lower tonewould be, in my opinion, impossible. (I have no scientific reasons to back this up, though.) Tom Sivak
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