jhughs
And now for an alternate view: "We tune to A-or somewhere around there. I never tuned; if you can find a strobe-tuner in the studio, I'll give you anything you want out of here.I'd just pick up the guitar, and whatever it was tuned to, I'd just tune the instrument to itself and have Mike tune to me, and we'd tune the synthesizer to it. Who made up the rule that an A string had to vibrate at 440, or whatever?" - Eddie Van Halen... of course HE can get away with that.
A-440 was well established as the standard before little Eddie was even a twinkle in his daddy's eye.
And he may have done that..... tuned like that back in the day. If you wish, there is nothing preventing that now.
Why tune to A-440 and not some random number... or just by ear? Good question. And the answer is you can tune to whatever you wish to tune to.
It's easier for me to answer why I tune to A-440. All my midi synths are set to A-440. So if I tune to 440 on guitar and later add a string or a pad or a piano or anything that is midi, I will not have tuning issues.
All my keyboards are set to 440 and all my tuners are calibrated to 440 as well.
If you are not using midi, it matters not to which number you tune. However, if you are recording....lets say, a bluegrass band, which doesn't use midi or piano, you would still want the tuning from one song to the next to be consistent.
Failing to tune to the same exact pitch between sessions would result in 10 to 12 songs on s CD that were not in the same pitch and to many listeners that would be noticeable. Something would sound off but they may not be able to tell exactly what the issue was. They would just know something wasn't right.
As for me, I always use a tuner if there is one handy. While my ears are sensitive to pitch, it's easier for me to let the tuner nail it every time as opposed to me trying to decipher those last few cents.
just my opinion..... tune as you wish.