Make an octave ukulele

An octave ukulele is a 4-string instrument tuned like a regular ukulele (gCEA, with the g being one octave higher than one would expect), but a whole octave lower. It is still played exactly like a ukulele but it sounds more like a guitar, with pretty deep bass. For those of you who actually want to accompany your singing and don’t want the instrument competing with your voice, yet are too lazy to learn a new instrument and set of chords. In this post, I tell you a simple way to make one starting from a baritone ukulele.

First of all, credit for discovering this trick goes to PortlyNight, and here’s the YouTube video where he tells you all about it. In essence, what you want to do is replace the baritone strings with guitar strings, taken from an extra hard tension set. Here’s one on Amazon. Then you take the strings from that set and put them on a baritone uke, in this order:

  • “4th string” (wound .030 inch) becomes the 4th “G” string, or you can use the original 3rd string, which is also natively tuned to G.
  • “6th string” (wound .045 inch) becomes the 3rd “C” string, or you can use the original 4th string (wound .035 inch).
  • “5th string” (wound .036 inch) becomes the 2nd “E” string.
  • “3rd string” (unwound 0.041 inch) becomes the 1st “A” string.

This arrangement, which differs somewhat from the one on the video, is based on the string equation, which is: frequency = SQRT(Tension/Linear_density)/Length/2. We know that a baritone ukulele has a 4th G string that is 0.030 inch wound, and the tension is around 14 lbs. Taking that as a starting point we can work out the other string diameters (provided they are of the same type), since the linear density is proportional to the square of the string diameter, and therefore the frequency is inversely proportional to the diameter. Now, a semitone interval is a frequency ratio of 2^(1/12) = 1.06. If we put that G string at the 4th position, to go from G to C (7 semitones) for the 3rd string implies a frequency ratio of 1.06^7 = 1.5, so that string should have a diameter of 0.030 x 1.5 = 0.0415 inches, which is the “6th string” of the guitar set. Going from G to E for the 2nd string is a drop of 3 semitones, which is a ratio of 1.06^3 = 1.19, so the string should be 0.030 x 1.19 = 0.0357 inches in diameter, which means either the “5th string” of the guitar set (high tension) or the original 4th string.

To get the 1st string “A” sound you could use a wound string that is thinner than anything you’ve got (the calculation, made in this other article, gives a diameter a tad under 0.037 inches), or you could use one of the unwound strings. The closest in the original set is the “B” string, with a diameter of 0.033 inches. To get that to “A” we need to lower the pitch by two semitones, which is a factor of 1.06^2 = 1.12, and the string diameter is 1.12 x 0.033 = 0.037 inches. The closest is the “3rd string” of the guitar set. The extra thickness will increase the tension a bit, which helps because the original B string is kind of floppy anyway, and keeping that kind of tension against three wound strings would make the 1st string sound rather weak.

Incidentally, it seems that people who did this kind of conversion ended up not liking the way the instrument sounds. Check out this YouTube video by Brad Bordessa, for instance. Probably because the lower pitch calls for a larger instrument volume, which you’re not getting from a ukulele.

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