Yeah, definitely, Brint! I use meantone throughout the tuning, at least for the 3rds. It doesn't make sense to me to
only sweeten the open tuning and not also tune the pedals/knees to yield the same interval across the whole instrument. I want all the most common chord positions to have the same setting for 3rds.
But I can't get all the way to meantone when it comes to the 5ths. So I compromise and use ET (+0) for 5ths.
The logic: everything is a tradeoff. In the case of 5ths, you're trading off sweetness for improving the '2 F#s' problem. Or vice versa.
* At one extreme, the 'sharp' end of the spectrum with JI (+2 over the root), you have maximum sweetness -- but also maximum distance between the 'two F#s,' and it's a real problem because the ideal target notes are a full 18 cents apart. Compensators on one or both F# strings are
really helpful here.
* At the other extreme, the flat end of the spectrum with meantone (-2.5), you have minimum sweetness -- you're sitting right at the border of too-flat yuck and couldn't go flatter even if you wanted to -- but at least the 'two F#s' problem is completely solved if you apply the -2.5 setting across the whole instrument (all pedal/knee chord positions); the target you want to tune the F#s to ends up being the same in the pedals-down world as it is in the open position.
My argument against using meantone for the 5ths is why would I want almost
every chord to sound noticeably less sweet, just to
completely eliminate the issue with the F# strings? In my opinion, that's letting the tail wag the dog. Or using a nuclear weapon to kill an annoying bee. There are more nuanced solutions to deal with the F# outage that don't negatively impact
every single chord you play that has a major 5th interval in it (i.e., everything except augmented or diminished). Unlike the 3rd interval where you have a big range to play with, that 5th interval is really finicky and must be either JI, or only
slightly flat of that.
So... I shoot down the middle of the two extremes and tune 5ths to ET (+0), which is a really common solution. It's a compromise that retains
most of the sweetness of JI. It also builds in a fail-safe aspect; strings can drift a couple of cents sharp or flat and they're still within that very narrow 4.5-cent-wide (or so) range of what's acceptable to the ears for 5ths. Using +0 also brings the 2 F#'s close
enough together that they can be dealt with, particularly the 1st string:
* The 1st string F# is tuned down the middle between the two 'ideal' targets, and is sweetened by using the slightest slant of the nose of the bar. It's a slight
forward slant (just 5 cents worth) in open position, and slight
back slant in pedals-down. Took 5 minutes of practice to lock it in.
* The 7th string is tuned to the sharper target, and I installed a compensator to flatten it in pedals-down. That string is used in several chord positions, and since it's not on the edge of the neck like the 1st string, you can't really bar slant you're way out of it when it's the
middle string within a grip. For those that haven't dealt with one, a compensator sounds like a complicated device, but it's just another pull attached to a pedal, like any other change under the hood... and worth it's weight in gold. The parts (another bellcrank, pull rod, nylon nut) costs around $40 and installed in a half hour. Recommended!
Even without the compensator, you end up with an acceptable Dmaj chord that's unsweetened ET, just like the guitar player's. And you
can forward slant the F#m position to get that one in tune.
* The C-pedal 4th string is tuned to the flatter version of F# to match up with the other strings in the pedals-down world (the C#, mainly), and that compensator is also in play slightly flattening the 7th string to perfectly match it.
Problem easily solved, and everything still sounds very sweet. The fail-safe aspects of the tuning (setting the 3rds and 5ths in the
middle of their 'acceptable' ranges instead of at the border) mean it's easy to sound good even when some strings drift a little off of their target or the temperature changes during the gig. This is the same principle behind B0b's excellent Quick and Easy tuning chart.
https://b0b.com/wp/2018/08/quick-and-ea ... ed-tuning/