b'cuz i said so? Failing that succinct explanation:
If the string hangs up on the bridge or nut, you'll go out of tune once it finally makes it's way over one or the other.
Example - the tuner pulls the string at 121 lbs between the tuner and nut. The string hangs up a little at the nut, and between the nut and bridge it's pulled at 120 pounds. Cool! 120 lbs means We're in tune. At some point, usually half a bar before your solo in front of that scout from Rounder, the string's tension will equalize along it's full strung length, and will make it's way down not to your intended 120 pounds, but more like at 119.13 lbs, and now you're in micro tonal territory, & wishing you were Fernando Saunders, with a fretless guitar no less.
Poor Fernando - had he only put a little bitta graphite on that nut...
Tune talk conjugation:
When all is well, "We" are in tune
When it is not, "You" are out of tune
Only kindly and elderly kindergarten teachers ever say "we" are out of tune.
And they're just being nice so "we" don't cry...
