But then the pattern across strings is also "relative" and only depends on the guitar tuning you're playing. For instance in the standard tuning, two neighboring strings are always a perfect fourth apart (five frets) unless they're the G-B strings in which case they're a major third apart (four frets). So if you know where you'd be playing a note on one string, that same note is just five frets back or four frets back on the next one. Which is again a totally "relative" framing that works for any individual note the same way. You can even figure out where you'd have to play if the tuning was non-standard. These patterns only have to be practiced a little bit, there's not really any need to learn them from scratch.
(If anything, I would want a "guitar learning" app to automatically come up with its own exercises, similar to ear training apps for learning to recognize intervals - and using something like a spaced repetition approach to evaluate how the user is doing.)
(If anything, I would want a "guitar learning" app to automatically come up with its own exercises, similar to ear training apps for learning to recognize intervals - and using something like a spaced repetition approach to evaluate how the user is doing.)