Not bein' snarky about those who have 'em, just doubtful I need one. Playing at home/recording, I get a "pure" note off our piano, and tune to that. Otherwise, I tune to the pitch(es) that work best for my singing, a particular song, etc. I use a clip-on tuner when playing somewhere I don't/won't have a keyboard to root on. In the band, we go from a piano/keyboard note as well. We can tell when a string or two have slipped/stuck and adjust pretty much on the fly. And/or we're tuning to the pitch that works best for a particular singer, song, etc. Seems to work okay. Sometimes we play with a guy who has a clip-on tuner and it's a pain to get him to stop fiddling with trying to match every string to its ideal open note. Plus, since every guitar is finnicky with how it best tunes, anyway, matching string to ideal note can mess up whether a particular guitar is in tune for a song in this or that key. What am I missing/messing up here?