Physical instruments can't be perfectly in tune even within themselves. Perfectly in tune is the preserve of electronic instruments. Even so I have a software synth that can adjust its own tuning within a chord to provide a more pleasing sound.
> Physical instruments can't be perfectly in tune even within themselves.
No, but they can sidestep the need to be perfectly in tune within themselves by allowing the player to produce notes unbounded by discrete steps or subdivisions thereof, e.g. fretless string instruments and trombones.
>by allowing the player to produce notes unbounded by discrete steps or subdivisions thereof, e.g. fretless string instruments and trombones
Then you have the problem that the player will himself be off, unwillingly, most of the time. Often more than the offsets of 12-tet to the "ideal" note.
> Then you have the problem that the player will himself be off
Maybe at first, but it takes all of two milliseconds to recognize "oh wow, I'm sharp/flat, I should move my hand a smidge further/closer". With more practice comes better muscle memory and better accuracy. Even high schoolers in marching bands can learn how to play a trombone in tune; a professional musician should have no trouble with that at all.
15 cents is huge. It's 15% of the way to the next note. Even 5 cents sounds noticeably out of tune. Trained musicians can easily tune to less than 2 cents without using tricks like beating to get even more accurate tuning.
Guitarists may be out of tune, but chances are more likely you're hearing a poorly intonated guitar. You can tune the open strings perfectly, but if your string scale-length deviates from what your fretboard expects, you'll have notes that progressively get more out of tune the further down the neck you play. You can't correct this with tuning, you need to adjust the tensions in your bridge saddles, and most amateur guitarists are afraid to do this.
Also you mention live settings, it depends on how big the group is I guess, but at smaller venues and smaller bands the stage monitoring is often so bad you can't hear your own guitar.
Guitars being out of tune happens because of the frets, not some lack thereof; most people tune each string with a tuner and/or by comparing to other strings, which means that some notes will be in tune and others will be very out of tune. This is one of many possible motivations (arguably the primary one besides ease of fingering) for tunings other than the "standard" EADGBE tuning: to change which subset of possible chords are in tune.
This is arguably a non-issue for fretless guitars, but those take more skill to play (and I'd imagine getting some chords perfectly in tune would entail nigh-impossible hand contortions even without there being frets involved).
Having to bend up to a given note each time you need to hit it will be slower and less precise.
Generally the bend is done after the fretted note is struck as well. I guess it would be possible to always pre-bend to a given alternate note if you wanted a constant tone, but it definitely seems like working against the grain of the tool versus just using a fretless instrument.
Eddie Van Halen was known to do this, though he was admittedly a freak of nature. He tuned the B string a few cents flat so that barre chords played up the neck would sound more in tune. If he needed to play, for example, a D chord in first position, he'd bend the D fretted on the B string slightly sharp.
There’s a video of a Van Halen concert where the synth track for Jump was played back at the wrong bitrate. Eddie worked furiously to find it on the guitar but couldn’t. It’s pretty wild to watch.
There are some players of guitars with a scalloped fretboard who do so to experiment with tempered tunings. It's definitely uncommon, but it's not unheard of.
Early electronic instruments, particularly before the 1980s had tuning all over the place, and you would have to wait 30 minutes to get anything resembling stability, even then nothing was guaranteed.
Think it would be possible to mockup some really interesting tunings/temperaments in BitWigs grid or Max4Live.
A tonewheel organ could be amplified acoustically, e.g. by physically touching an appropriately sized resonant chamber to the wheel when you press a key. The exact size of the resonator does not matter because it's mode locked to the wheel, which turns at a speed determined only by the gear train. Tonewheel organ gears traditionally do not have perfectly accurate tuning, but there's no reason they couldn't be built to match any tuning system within the limits of human hearing (at greater cost and complexity).
