I got a chance to play with an Bass Guitar* recently. I am starting to understand many things about bass players that puzzled me in the past.
First, though, was mild surprise at how quickly I figured out "where the notes are." The bass is tuned in fourths, and unless you have an "extended" bass, the strings are in the same order (but sound an octave lower) than the four lowest strings on the guitar.
So a consistent interval, and certainly simpler than the reentrant tuning of a soprano or concert ukulele, but still it takes only moments to adapt and figure out where the next note you want it. I still don't get, in fact, why there are fingering charts for single notes (as there are, and many indeed, for the violin). But then, I'm not usually sight-reading. So I don't know I'm on a G, and I don't have to go through figuring out that the next note will be a B, so where is that...instead I just know I need a note that's a seventh above, and I go there.
In any case certainly beats the fork fingering of a recorder (where half your notes require a combination of fingers with holes left open at various places along the body).
I did somewhat "err" in going for thumb plucking at first. This is uke instinct; you hold up the Uke with your fingers so thumb pluck or strum is easiest. But turns out some bass guitar players use this to sound more like an upright bass -- and by the time I'd read this, I'd already discovered the associated trick of using the heel of your plucking hand to dampen the strings (you rest it on the bridge, in fact).
Fingers work, too, but for that I needed to use the neck strap. In any case, finding the simpler walking bass lines and so forth were dead simple.
Which is the first thing learned; getting them to sound clean is another issue entirely. Like violin, every tiny bit of noise is amplified. Every hammer-on and lift-off is audible, as is every time you brush against another string. Plus unlike the violin, where the sympathetic vibration of the open strings is part of the desired sound, those fourths really clash if you don't make a point of muting the strings you aren't using.
The second thing is how hard it is to hear. I couldn't even get my tuners to recognize it at first. You really need an amp to hear yourself well enough to play.
And it is really all about tone. The difference between the right tone for the song and the moment and the almost right tone is like Mark Twain's "Lightning and lightning bug." And, yeah. You don't hear that tone -- the essential elements that make that tone -- without some serious horsepower in your bass amp.
A 10W practice amp is just barely enough, and that's with it cranked up to max.
So in just a little playing around I suddenly have way more sympathy for the bass players and their amps and their constant adjustments in the name of tone.
Heck; I'm not even sure that you really find your notes through what comes over headphones. The violin communicates when your intonation is right in part through vibration that you feel directly through your skin. I can believe that you know what pitches the bass is making -- at least on the lowest string -- by the low frequency vibrations you feel in your very bones.
The bass is more like a piano than it is like violin or woodwind or brass; you can pretty much produce a note-like object the first time you pick it up. But like all musical instruments, making that note sound good, and adding expression to the performance, is lifetime study.
*sorta bass guitar. Details to follow.