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Due to the fact, there is no standard for CBG construction regarding the number of strings or the tuning, I am writing this information to help builders who are new to music, and offer suggestions that will make their builds function better from a musical stand point.
The easiest way to tune your CBG is by using a headstock "clip-on" electronic tuner. They are very inexpensive. They come in two different models. A standard model that only tunes the standard 6 string guitar notes, and the one I suggest, the Chromatic model, that can tune all the possible notes.
Use standard guitar strings (medium gauge)
Guitar strings are designed to produce a certain pitch (note) when they are tuned to a specific tension. Using an average scale length (the distance between the nut and bridge) of about 24.75 inches, from low to high, the 6 strings are tuned:
E A D G B E (numbered low to high 6 5 4 3 2 1)
Use Open Tunings
A standard guitar uses a compromised tuning that allows the guitar to be extremely versatile. It can play in all 12 different keys of music. Another method used in Folk and Blues music, Open Tuning, simplifies the instrument by tuning to one key and using a basic three note chord.
Open G Tuning (Spanish Tuning)
The Major Scale notes for the key of G are: G A B C D E F# G (Tones numbered 1 2 3 4 5 6 7 8)
Open G Tuning on a 6 string guitar low to high is: D G D G B D
It contains tones 1,3,5 (G, B, D) from the G Major Scale that are required to make a G Major Chord.
Using the configuration of the full 6 string guitar Open G Tuning as a guide, CBGs with various numbers of strings can be tuned so they utilize the same finger positions on the fretboard. This becomes a very practical approach because the same understand of the fretboard can be applied to any instrument, regardless of the number of strings. Uke, tenor guitar, banjo...
The simplest instrument utilizing only one string is called a Diddley-Bow
Tone 1: String 5 (A) tune down to G or
Tone 1: String 3 (G)
A partial Major Chord can be formed by using:
Tones 1 / 5: String 5 (A) tune down to G / String 4 (D) or
Tones 1 / 3: String 3 (G) / String 2 (B)
Know as G5 Tuning, only two tones, but three strings
String 5 (A) tune down to G / String 4 (D) / String 3 (G) or
A full G chord
Tones 1/3/5: String 3 (G) / String 2 (B) / String 1 (E) tune down to D
String 4 (D) / String 3 (G) / String 2 (B) / String 1 (E) tune down to D or
String 5 (A) tune down (G) / String 4 (D) / String 3 (G) / String 2 (B) or
String 5 (A) tune down to (G) / String 4 (D) / String 3 (G) / String 1 (E) tune down to (D)
Standard bluegrass banjo tuning (use banjo strings)
Tones 1/5/1/3/5: gDGbd
Tones 5/1/5/1/3/5 Open G Tuning DGDGBD
CD1 Vestapol Tuning (Open D) for 6 string & 3 string cigar box
CD2 Spanish Tuning (Open G) for 6 string
CD3 Comparing Vestapol and Spanish Tuning for 6 string
CD4 Cigar Box Guitar for 3 string (GDG)
CD5 Cigar Box Guitar for 4 string (DGBD)
CD6 Cigar Box Guitar for 3 string Part 2
Fretless info and fretted Devil's Tuning Method. The same strings tuned GDG (CD 4), retunes to ADF# (Open D) provides a "Moveable Chord Method" that fuctions very similar to the method used on a standard 6 string guitar.