Thirty-First English Trigesima Prima Italian

Despite being listed in three different stop dictionaries, this is not an independent stop, being much too high-pitched, but is a rank found in mixtures. Its pitch is 2/5' when reinforcing the 8' harmonic series, and 4/5' when reinforcing the 16' harmonic series. Irwin claims that this rank sounds �four octaves and a third above the keys depressed ... at the approximate pitch of the twentieth harmonic�. Irwin has it backwards. This rank, if it is to be of any use at all, must sound at exactly the 20th harmonic, which is only approximately four octaves and a third above the fundamental.

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