Of course, a higher action will allow a player to pick the strings harder, thus imparting more energy into the strings when the player desires more volume, without the buzzing that may occur with a lower action. I've heard the statement that "raising the action will also increase the volume of a mandolin" many times but I've never really heard a good explanation of why that is so. I surmise that any difference in tone is associated with tiny, almost imperceptible collisions of the vibrating string and the frets. associated with raising the action by roughly 0.01 to 0.1 inch - which is what we're talking about here when we back off a tad - is WAY to small to account for changes in tone. The actual change in string break angle, string tension, etc. Put another way, if you manage to hear a difference by raising the action ever-so-slightly, then the chances are good that the strings were beginning to strike the frets, every so slightly, at the lower setting. This is a matter of geometry and physics. In principle, there should be no sonic benefit to raising the action beyond the point where fretted strings don't strike the frets or fingerboard when plucked. But we're both talking about the same thing. But for you, this same action corresponds to a "slightly-higher-than-lowest" setting. If so, then this whole discussion just comes down to a matter of terminology, and how one chooses to decide when low is low enough! For me, backing off just a tad and raising the bridge by a fraction of turn from the point where buzzing begins IS the "lowest possible action" - because, as a matter of definition, that's just how I think about it. So, going JUST A TAD higher prevents even the occasional collision, and sounds "sweeter" to your ear. This, of course, may be hard to hear on the fly, but it robs the strings of their optimal tone. It may well be the the "lowest possible" setting is, in fact, just a bit TOO low because the strings occasionally hit the frets (but only barely!), particularly under slightly heavier picking. You seem to be comparing what one might call the "lowest possible" action setting (no obvious buzzing, and with everything else set up properly) with a "slightly-higher-than-lowest" setting (you called it "a little bit higher"). I think there's a simple explanation for your observation. It's not something anyone would call high or even medium action. And I'm still talking about a very tiny increase in height over minimum-before-buzz setting. I'm not sure what causes the higher volume and subjectively better tone, but it might be the increased break angle over the bridge. This may vary by individual instrument too. My mandolin just sings a tiny bit sweeter at that point, compared to sneaking it down to the minimum height before buzzing. However, I do notice a slight improvement in volume and tone when I have the action set a little bit higher than the lowest I can get it without buzzing, on a neck where everything else is near-perfection in dressed frets, truss rod relief, nut slot height, and so on. It's definitely true that the lower you can get the action without buzzing, the better the intonation will be. This is both a matter of ergonomics and musical accuracy. But the action in a properly set up instrument should be NO HIGHER than absolutely necessary to avoid buzzing. This will vary from instrument, and from player to player, of course. In fact, ALL fretted instruments should be set to have the lowest possible action that is consistent with no buzzing (i.e., noise due to intermittent fret contact by the strings after being struck), under normal conditions of play by their user. It's also true that lower actions tend to have less systematic problems with intonation. And folks like Mike Marshall and Chris Thile and Joe Walsh and Sierra Hull all go for lower actions.
![high action strings high action strings](https://www.native-instruments.com/typo3temp/pics/img-action-strings-dd73b71edec8541942f562777cf69e33.png)
![high action strings high action strings](http://3.bp.blogspot.com/-SjVFGmlea38/Uhv5VMR9KmI/AAAAAAAABU4/hA3wIQxBvao/s1600/IMG_0106.jpg)
But Sam Bush's preferred action is moderate, and not that high. A high action was certainly true of Bill Monroe, and also of John Duffy. Second, it's just not true that most of the "experienced pros" desire high actions. If you push hard enough, yes, it may be necessary to raise the strings a bit, but not excessively. Heavier strings and a firmer right hand lead to louder volume. First off, high action alone does not necessarily equate to louder volume. That said, I don't believe that you are correct to write that "high action is usually desired by experienced pros for banjo-killing volume." Not so. The advice you gave is spot on! One should learn on instruments that are properly set up and upon which playing feels comfortable. Standard tuning with high action is usually desired by experienced pros for banjo-killing volume. Learn on instruments that are setup to feel RIGHT for you, not DIFFICULT.