When TAB is written, and a capo is needed on, say, fret 2, does the tab get written as if the barre formed by said capo is the actual fret it's on, or does that fret become the 'open' string? In other words, would a note on the 2nd fret be labelled 0 or 2?
It would make sense if capo placing was called 0, as it'd be easy then to transpose anywhere, but, not being a fan of tab, so somewhat ignorant, I felt there was a question here.
It can vary, but almost always I see tab for capo written “transposed”, by which I mean a string played “open” to the capo is marked with a 0. Playing two frets above the capo is noted with a 2.
This follows the most common convention for chord symbols and score notation when using the capo.
Todd's answer is correct. I will add that when a solo or melodic line is transcribed along with a rhythm guitar part, sometimes the rhythm part will be notated with fret 0 at the capo, but the lead line will not. This is especially common if the solo happens on the higher frets, as it's simpler to not do the math. Usually the transcriber will note this. Same exception applies to bass parts, the bass guitar will usually not use a capo.
