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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