maybe im just dumb but....

[defzeppardica]

what limitations are not letting us easily track a normal guitar signal. Why can't I plug my guitar into my computer and play something and have my computer make tabs out of what I played? Is this something that we know will eventually come out or is it just an impossibility?

[anchovie]

It's not impossible, it would just be a very complicated piece of software to write.

Pitch detection is possible now (the firmware in digital harmonist effects is obviously capable) but for chords you would need code that could distinguish between the harmonics present in a vibrating string and the notes that you've actually strummed.

As for signal-to-tab, once you've got the ability to detect single notes and the notes that make up chords you'd also need some kind of artificial intelligence that could take those notes and decide which fret positions would be the most logical ones to use, based on the abilities of the human hand and the fact that you can't play two notes on one string at the same time.

Then of course there's technique too - did that bend come from a finger or a whammy bar? Pinched harmonics, palm mutes, etc.

Like I say, not impossible. But I wouldn't envy the masochistic programmer that took on the task!

[FiveseveN]

Two words: hexaphonic pickups 

[Mark Hammer]

what limitations are not letting us easily track a normal guitar signal. Why can't I plug my guitar into my computer and play something and have my computer make tabs out of what I played? Is this something that we know will eventually come out or is it just an impossibility?

It's the same problem faced by the human ear: how do you know what frequencies go with what fundamentals, especially when all auditory information is coming in through the same singular point of entry?  True, we DO have two ears, but you can still identify multiple notes and pair them up with their respective harmonics using only one ear.

If the harmonics were all higher order, then it could be a simple matter of some lowpass filtering to carve them out and the computer could simply detect the pitch of what's left.  Hell, I had a little real-time analyser cartridge for my Radio Shack Color Computer 20 years ago that did a great job detecting the frequency content in 31 bands, so it couldn't be THAT hard to do. But keep in mind that the RTA I had back then (still somewhere in the basement along with the "computer museum") only had to detect frequency content in a general sense.  It did not have to determine if content in different bands "goes together" or is part of a different note-event.  The problem is that in between your low E and high E, you have all those other damn strings.  Lower harmonics from the low E overlap fundamentals on those other strings, and lower harmonics from the "in-between" strings overlap with the fundamentals of the high E.

This is the principle reason why a hex pickup is recommended.  At that point, the decision the software has to make is "What is THE fundamental in all of this?", rather than "What potential 6 fundamentals might be in progress here?"  A divided pickup also lets one apply filtering intelligently, so as to render the "which note" decision even easier.

[defzeppardica]

so with a normal guitar pickup.... it would be possible to write DSP code to split the signals for each string to manipulate each one separately? it would just take some crazy coding and knowledge of the different harmonics and what not?

[Seljer]

so with a normal guitar pickup.... it would be possible to write DSP code to split the signals for each string to manipulate each one separately? it would just take some crazy coding and knowledge of the different harmonics and what not?

you might get as far as splitting up the different notes in a chord.....but then how are you going to know if you're playing a D open or at on the 5th fret A string or at the 10th fret E string? what if you play the same note on 2 strings?

I guess you could get close with some kind of analysis of the harmonics (maybe compare the signal coming from the neck pickup and from the bridge pickup?) but I predict it'd be rather unreliable....the hex pickup makes it a hundred times easier