[Harp-L] Ghost notes on harp

["John F. Potts" <hvyj@xxxxxxx>]

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.