Semitone calculator

One hundredth of a semitone, so 1,200 cents to the octave. It is the unit tuners and pitch-correction plug-ins use, because whole semitones are far too coarse to describe how in tune something is. Trained listeners notice a steady tone that is off by roughly five to ten cents; drift of 20 cents or more reads as out of tune to almost anyone.

About 31.8 cents, roughly a third of a semitone. That is well inside a semitone, so the notes keep their names, but it is far enough that instruments tuned to the two references cannot play together. Enter 432 as the starting frequency and 440 as the second one to see the figure yourself.

Because equal temperament divides the octave into twelve identical steps, which is a compromise that lets every key work. A pure fifth is 702 cents against equal temperament’s 700, close enough to pass. A pure major third is 386 cents against 400, and that 14-cent gap is why a sustained major third on a piano beats slightly while the same chord sung by a choir does not.

For a solo voice, a few semitones in either direction is usually safe with a modern algorithm, and beyond that the formants start to move with the pitch, which is what produces the chipmunk or the monster. Percussive and noisy material tolerates less; sustained tones tolerate more. Shift the whole arrangement rather than one part when you can.

Not directly, because a note name depends on the tuning reference. What it does do is the arithmetic behind that answer: enter your reference, say 440 Hz for A4, and the measured frequency, and the semitone count tells you how many steps away the note is and by how many cents it misses.