Tips for guitarists playing Joni songs on acoustic guitar
by Dave Blackburn
First, use a guitar with a very firm neck if you have a choice (the Taylors are the best as they have a special neck joint that doesn't flex when the string tension is altered). A lesser guitar will always fight you when the neck tension is altered.
Second, use custom string sets if you have to. Elixir sell Light/Medium sets which are heavier on the bass strings and lighter on the treble, ideal for Joni tunings. A typical Joni tuning might drop your bass strings by a third or fourth so you can expect them to be floppy. But heavier guage strings will help as they are higher tension to start with. You can even buy strings for baritone guitar nowadays which would be perfect as they would be tuned to the tension they were designed for BUT the slots on the nut would have to be widened. So decide how far you're willing to go with this stuff and whether you are prepared to hack into your instrument. Joni rarely tunes upwards from standard by more than one semitone so string breakage is unlikely but you can use light guage strings for your top two strings if needed.
Third, if you use a capo, buy a "G7th" brand capo. Don't use the Kyser or Dunlop. The G7th is the only capo that lets you capo up without stretching your strings sharp.
Fourth, practice playing the songs with a light left hand touch. When the strings are tuned low you are basically stretching the notes sharp as soon as you fret them. Learn to press the string only to the fret and not beyond towards the fretboard wood.
Fifth, and this is something that takes patience, use a tuner (must be chromatic) to get you in the zone but finish by ear. The bottom string when open must usually be tuned flat by as much as 12-15 cents for it to sound somewhat in tune when you fret it. As the tension on the strings is now wildly different from what they were designed for, they will behave strangely and probably buzz. If so you may need to raise the action slightly. Sometimes Joni just let the strings buzz regardless (see "The Wolf that lives in Lindsey") The open bass string may sound flat but the fretted string sharp. You have to find a happy medium and be prepared to live with it not being perfect.
Finally, you'll notice Joni favored a lot of chorus or flanging on her later albums (and even had the Roland Jazz Chorus amp built for her in 1976). Chorus helps a lot by making the pitch center more swimmy and thus hides many of the guitar's tuning problems. I'd recommend using some chorus. (On Hejira most of the tunes used double tracked guitars and chorus and even Rotary speaker effects for modulation so she was figuring out how to make her tunings sound really huge.