Playable LEGO Upright Bass
The LEGO Bass... A 9 1/4" Scale Playable Upright Bass
The LEGO Bass may be the best rubber band guitar in the world. An O-ring sounds pretty good if you add a piezo pickup and a good bass amp. I made a two-string non-LEGO version of this first, but the LEGO version is better. This is what it sounds like:
Playing the LEGO Bass
It's almost entirely LEGO Technic, no glue. The exceptions are the silicone cord strings. Originally they were cut O-rings, probably Buna-N rubber. In this video, the two lower strings are silicone O-ring stock, McMaster Carr part number 5229T51. The pickup under the bridge is home-made from a piezoelectric disk with a heavy weight glued to the back side. The high impedance pickup is amplified by an op-amp preamp circuit with bass, treble, and volume controls (the three grey wheels around the bottom section).
Preamp for the piezo pickup.