This week we consider some technical details...

1) Consider the frequency that our strings vibrate at (in concert tuning where A=440Hz).

7a = 55 Hz
7B = 61.7 Hz
6E = 82.4 Hz
5A = 110 Hz
4D = 146.8 Hz
3G = 196 Hz
2B = 246.9 Hz
1E = 326.6 Hz

So what you ask?
- If you use an EQ unit/ EQ plug-in then you can cut & boost areas of your sound in a more precise manner.
- If you are looking to buy a microphone or speaker then it's frequency response needs to cover the 7string's full range.

2) Now consider the tunings 7A 6E 5A 4D 3G 2B 1E & 7B 6E 5A 4D 3G 2B 1E
- The intervals between A & E = 5th, A & D = 4th, A & G = minor7th, A & B = 9th. These intervals represent the recipe for a A Minor 9th chord.
- The intervals between B & E = 4th, B & A = minor 7th, B & D = minor3rd, B & G =minor6th. These intervals imply a B Minor b13th chord.

So?

Guitarists can & do experiment with the tuning of their strings to change these chords and by changing the tuning, so the frequencies change...

3) Food for thought:
Every object has a unique natural frequency of vibration. A periodic force occurring at the same frequency as the natural frequency of vibration of an object may cause the object to vibrate. This is called mechanical resonance. This is the principle that enables a glass to be shattered by sound. Makes you wonder what potential our instruments actually possess...

Recommended listening:
Brothers in Arms live by Dire Straits
War by Joe Satriani

see also:

Guy's site: http://www.7string.org/

And previous GNW articles:
http://www.guitarsite.com/newsletters/010430/7.shtml