[Harp-L] Ghost notes on harp



v
Here's an excerpt from an article on Pat Missin's web site that explains what he, I and Iceman are referring to as ghost notes and Winslow calls summation and difference tones. Winslow is probably right, but i've also heard others refer to these "Tartini tones" as ghost notes. Some players are adamant that the ghosts notes produced on equal temperament harmonicas sound harsh or unmusical, but that has not been my experience. Playing the 7-8 draw double stop on an ET harp will produce the ghost note an octave below the 2 draw as Pat Missin describes at the end of this article. Try it--it's spooky. There are sound samples on Missin's site for this particular ghost note.


JP

From Pat Missin's web site:
Whenever you play two pitches at the same time, additional pitches are produced, called combination tones, ghost tones or Tartini tones - the lower one is the difference or differential tone; the upper one is the summational tone. The frequency of the difference tone is the difference between the frequencies of the two original pitches; the frequency of the summational tone is the sum of the frequencies of the original tones.


So, if you play a note of 440Hz at the same time as one of 660Hz, you will get additional pitches of 220Hz and 1100Hz. Or, to put it musically, if you play an A at the same time as the E above it, you will get a pitch equal to one octave below the original A and a C# above the E. Similar "ghost" notes are produced by other intervals. On a justly intonated harmonica they are harmonically related to the generating pitches, but on a tempered tuning the combination tones are "out of tune" and often produce very harsh effects. This happens with all instruments, but the effect is particularly noticeable with the harmonica.

On a harmonica, the difference tones are usually much stronger than the summational tones, although the summational tones contribute to the overall timbre or tonal quality. In fact, in the top octave of the harp, the difference tones are almost as loud as the original notes. The difference tones can be greatly emphasised by the player's technique, particularly if there is a mike and amplifier involved - the use of combination tones is one of the "secrets" to getting a big amplified tone. If you alter the frequencies of the original notes by bending, the pitch of the difference tone will also change. This can produce an interesting sound, but it can also be quite distracting. The classic example of difference tones in an amplified blues harp context is by Corky Siegel on the Jimmy Reed tune "Honey Hush", from the album "The Siegel-Schwall Band".

The easiest way to demonstrate them is to take a high pitched harp - an F harp is ideal. Play first 7 draw, then 8 draw. Now play both notes together. Depending on how well the harp is tuned, you should be able to hear a note which sounds an octave lower than 2 draw on the same harp - that is the difference tone.







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