The electric bass has been occasionally used in microtonal music. Experimental composers often obtained unusual sounds or instrumental timbres for example through the use of overtone- and sliding techniques. Bass guitarists playing microtonal music may be instructed to tune the instrument in unusual ways. Following tools (taken from ther chapter 'microtonal bowed strings') are also important to make microtonal string music work on (fretless) bass guitar.
1. Scordatura: If you're going to be using the traditional notation system or a variant of it, specify that the strings be tuned to the scale system in question's versions of A, D G, etc. to give the players familiar notational home bases to work from. Try to make the scordatura somewhat distant from the correct pitches for maximum effect, however, because broken-in string instruments "ring" for the notes they play often (in 12), and the scordatura will have the effect of disorienting the string player's instinctual seeking of the resonance.
2. Fingerboard marking: Tapes are the most awesome (because they're color codable), but chalk works too. Players respond to them well because most of them learned to play with tapes in elementary school. Provide tape to the players, debunking any myths that it will affect the sound or damage the instrument. If it does leave some sticky residue, tell them to wipe it off and suck it up. If you don't trust your string players' ears, or the part is technically challenging, color coded tapes are plainly the easiest way to get it in tune fast.
List of Microtonal bass players
Brad Catler - http://www.microtones.com/site/bios/brad_catler.html/
Abdullah Shakar - http://www.facebook.com/abdulbass.shakar/
Hansford Rowe - http://www.hansfordrowe.com/
John Starrett - http://www.microtonal.freeservers.com/
Jeroen Paul Thesseling - http://www.jeroenthesseling.com/
Jurica Jelic - http://www.juricajelic.org/
Tútim Dennsuul - Ksenthings
Dywane Thomas, Jr., known as MonoNeon - https://www.youtube.com/channel/UCrqcwlUjeTQ6NO8e6M2PL-A