Apple Logic Pro 9 - Manual (Page 1229)

Hermode Tuning can help with this problem: it retains the pitch relationship between
keys and notes, while correcting the individual notes of electronic instruments, ensuring
a high degree of tonal purity. This process makes up to 50 finely graded frequencies
available per note, while retaining compatibility with the fixed tuning system of 12 notes
per octave.
How Hermode Tuning Works
Frequency correction takes place on the basis of analyzed chord structures.
The positions of individual notes in each chord are analyzed, and the sum of each note’s
distance to the tempered tuning scale is zeroed. In critical cases, different compensation
functions help to minimize the degree of retuning, at the expense of absolute purity, if
necessary.
For example:
• The notes C, E, and G form a C Major chord.
• To harmonically tune these, the third (the E) needs to be tuned 14 cents higher (a cent
is 1/100th of a tempered semitone) and the fifth (the G), needs to be 2 cents higher.
It should be noted that Hermode Tuning is dynamic, not static. It is continuously adjusted
in accordance with the musical content. This is done because, as an alternative to
tempered, or normal, tuning, fifth and third intervals can also be tuned to ideal frequency
ratios: the fifth to a ratio of 3:2, the major third to 5:4. Major triads will then sound strong.
With clean (scaled) tuning, Hermode Tuning changes the frequencies to values that are
partly higher or partly lower.
1229 Chapter 43 Project Settings in Logic Pro