Make your own Planck!
Steven Sexton, a guitarist from the USA, has designed and built a simple, melodious -sounding 7-string tapping instrument. He did not want to waste his time with the patent application and money and provides a manual for assembling available as open source.
Sounds on the demo video, the great.
A standard 25.5 "(647.7 mm) scale length. The actual length of the instrument is 36 inches (914.4 mm). It consists of two layers of poplar wood, 8-mm-thick frets, selfmade 7-pin pickup and the usual hardware. Much Music for less money!