Five string tuning. Strange idea? Indubitably Sound quite nice? Presumably.
low E: Bb (Tonic)
A string: none
D string: Major 3rd Higher (noted D)
G string: Major 3rd Higher (note D)
B string: the Dominant 5th (note F)
E string: the 9th (note C)
It's just a fun way of exploring soundmaking options with five strings until I replace the broken A string.
Also provides perspective on the usefulness of thinking about notes regards to where they are placed compared to the tonic. This allows for melody and harmony ideas.
To my sense of hearing, these notes and tuning in fact sound slightly more enjoyable when tuned not exactly to concert pitch Bb as the tonic, actually about 30 percent higher towards the note B.
Playing notes: this tuning does require some regular maintenance to keep in tune.
12th fret harmonics of these notes as a chord sound amazing.