I presume that this topic refers to Fretless Electric Bass, and not early hybrid URB instruments. The early URB's were fretless like an upright but were played vertically so not really in the area of interest for this topic.
Find the first fretless electric bass (horizontal) and you will also find the first fretless bass player. So this post also covers finding early fretless basses.
Here is another reference to Bill Wyman early modification.
http://en.wikipedia.org/wiki/Bill_Wyman
It does not mention a specific year but I understand that it was 1961.
To the best of my knowledge, there were no production electric basses prior to 1935. see
http://www.historylink.org/essays/outpu ... le_id=7479
When Audiovox finally produced Tutmarc’s next invention -- the #736 Electronic Bass Fiddle -- the refined instrument’s main innovation was as a string-bass instrument designed to be held in the now-familiar horizontal position rather than the traditional vertical upright position. So because of its electrified nature, fretted neck (unlike upright basses), and truly compact size, this revolutionary instrument can be considered the world’s first solid-body electric bass guitar.
More information on this early bass here.
http://www.stratcollector.com/newsdesk/ ... 00103.html
And here.
http://www.vguitar.com/brands/details.asp?ID=48
I actually played with Bonnie Guitar (married to Paul Tutmarc) in the early 1970's and heard this history first hand from a witness. This was a horizontal FRETTED instrument. If someone pulled the frets from this early electric bass, and that person could be identified, I think we might have the name of the first fretless bass player. Unfortunately, Bonnie or other members of the family never mentioned Paul producing a fretless #736.
Other electric basses from the period prior to 1951, dating from Paul Tutmarks' early electric bass invention in 1935 were mostly prototypes or one offs, meaning that there were very few electric basses during that time. If there is a single Fretless electric bass pioneer, it would most likely be during that era. Most of the upright players shunned the instrument, the most likely users were guitarists crossing over to bass. These players were (IMHO) not likely to adopt Fretless since that would put another layer of technique on a guitarist.
This site
http://www.ultimate-guitar.com/columns/ ... uitar.html says...
In 1965 came the first fretless Bass Aubi from Ampeg and in 1968
Actually AUB1 in 1966, this was the bass I played from 1968 on.
This quote from:
http://www.prawnsong.com/bullboard/show ... ge=6&pp=20 pretty much clears the fog.
"In How The Fender Bass Changed The World, Jim Roberts states that Bill Wyman made the first known fretless bass guitar in 1961 by converting an inexpensive Japanese fretted bass. This fretless bass can be heard on The Rolling Stones songs such as "Paint it Black". The first production fretless bass was the Ampeg AUB-1 introduced in 1966. Fender introduced a fretless version of the Precision Bass in 1970. Fusion-jazz virtuoso Jaco Pastorius created his own fretless bass by pulling the frets out of a sunburst Fender Jazz Bass, filling up the holes with wood putty and coating the fretboard with epoxy resin."
So, according to available information, Bill Wyman is the first fretless electric player (1961), but I strongly suspect that at least one other less known musican had the same idea very much earler.