The electric bass guitar was invented by Seattleite Paul Tutmarc in 1936 and sold locally from at least early '37. It was a short-scale (about 30", or three more frets than a guitar, like most short-scale basses of today), solid-body, neck-through -made, fretted, mag-pickupped, horizontally-held instrument tuned E1A1D2G2. Both it and its late '40s reissue by Tutmarc's son Paul Jr. AKA Bud failed to make any impact in the potential market, went essentially unnoticed and today survive in less than 20 specimens (only two of which are Bud's version).
Leo Fender's original Precision (single single-coil pickup, Tele headstock, later reissued in 1968 IIRC under the "Telecaster Bass" designation) came out in 1951. Solid body, long 34" scale (guitar scale plus 5 frets, rounded up a skosh). While it initially struggled to be accepted, at no point did it and its Fender descendants not outsell their competition by far - after a competition started to exist at all, in 1952 with the introduction of Kay's K162 electric bass (the so-called "Howlin' Wolf bass").
However, those few models that tried to get a slice of the budding market created by Fender didn't follow Leo's recipe too closely: the Kay was short-scale and hollow-body, the Gibson Electric Bass (later retconned EB-1) from 1953 was a short-scale solid-body violin-shaped instrument with the option to be played vertically on a screw-on endpin; Höfner's 500/1 bass (1956), later to become the iconic "Beatle bass" for many of us, was, beside short-scale and violin-shaped, a hollow-body one and actually built with violin-making principles and techniques, to a point. Only in 1957 was another long-scale bass issued, the Rickenbacker 4000; it was neck-thru like most Rick basses that followed (thus reintroducing the design in bass-dom after the Tutmarcs' forebears) and, based on the addition of 5 frets' worth of length to their guitars (again with a little correction) it ended up slightly shorter than 34" Fender scale: to wit 33.25". (In fact, if we only look at the number of models brought to market, not individual sales which were dominated by Fenders as mentioned, long scale only became the undisputed standard in the early '70s). (EDIT: as far as deviations from 34" scale norm, in 1959 early Carvin and Supro basses appeared which were in ~25" guitar scale! More Japanese-built mini-basses came out in the following decade.)
Now, what was Danelectro's 1956* take on the electric bass guitar concept?
(* Some Internet sources say 1959. Anyone in possession of a copy of Doug Tulloch's
Neptune Bound - I don't own one yet - feel free to correct any and all inaccuracies; ditto for errors in the general timeline above, and below.)
The UB1 (and the better-known 2-pickup version the UB2): a single-cutaway, short-scale (Dano- guitar-scale plus three frets, or a smidge less than 30"), semi-hollowbody, 6-string instrument with close-spaced light-gauge strings tuned E1 to E3 - essentially a long electric guitar tuned an octave lower. It is my understanding that, for a couple years until the introduction of the Longhorn bass (the 4-string version - a 6-string one was also available), the 6-string bass as described above was
the Danelectro bass, as in, the only one in their catalog.
Now, since the Dano cut itself a significant niche in the Nashville pop-country scene of the time, where the practice of having two basses in the rhythm section, one upright and the other a Danelectro 6-string (AKA "tic-tac" bass) playing mostly the same, pre-arranged bassline in unison was established, other manufacturers came up with their own version of the instrument, like Gibson with the EB-6 and the Fender VI, later Bass VI, the most famous of all.
If you mentioned a "6-string bass" at the time, when the aircraft-carrier decks of nowadays** were still a speckle in Anthony Jackson's eye (he conceived his "contrabass guitar" in the mid-'70s but they only became sort of widespread in the late '80s), you'd either get blank stares or nods of understanding from musicians who got that you were talking about short-scale narrow-spaced EABGBE things.
(** J/K folks, I don't play but nevertheless like modern BEADGC sixers, they're awesome.)
Many of these instruments were used by guitarists for low-pitched lead guitar duties rather than basslines, either as-is or retuned higher with lighter-gauge strings: the so-called "baritone guitar", for which dedicated, shorter-scale instruments became somewhat common come the Nineties (plus-1-fret 27" and plus-2 28.5" are popular scales), but, and this is important, was a concept that was an offshoot of the old-style 6-string bass and didn't exist before it, except perhaps for acoustic one-off custom affairs.
^Too long, didn't read: dude, they've been around since forever!
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Couple extra comments:
Squier reissued the VI a couple years ago, and there are a number of alternative choices from other makers, so there are probably more out there now than at any point in the past. Predictably many adopters will end up not knowing what to do with them. [...] I've actually written extensively about the topic - here's an old post of mine, about as lengthy as this one so I'll just link to it if you care checking it out:
NBD... Ibanez SRC6 crossover... LOVIN IT!
[...]
[Nth EDIT - a separate section for TB thread links.
A recent thread - if you forum-search for "bass VI" in thread titles more should come up - about the possible uses of it:
How to use a Bass VI in a band?
Another one:
Who here uses a Fender Bass VI as an actual bass?
Four megathreads on this type of instrument:
The Short-Scale Six-String Clubfor the original six-string basses!
The Short-Scale Six-String Club Part 2- for the original six-string basses!
The Short-Scale Six-String Club Part 3 - for the original six-string basses!
The Short-Scale Six-String Club Part 4 - for the original six-string basses!
Two specifically about the Squier re-issue:
Squier Bass VI. At last an affordable, somewhat correct VI!
Official Squier Vintage Modified Bass VI Club ]