E and D are one letter apart. A and G, too. Your index finger on the second fret of the D string is an e. Rhymes with the E string. Your index finger on the second fret of the G string is an a. Rhymes with the A string.
Octaves.
Any note you play on the G string will have an octave echo, two frets down, on the A string. That's one finger down, because every finger covers two frets. Want to jump the melody an octave down? Jump down two strings, one finger up. An octave up? Up two strings, one finger down.
Try it. Yankee Doodle went to town .... Starts on the D string, ring finger. Okay, that's E string, middle finger.
Next note, low version? An open A string. Whoops. Well, that's okay, you know where the high version starts on the E string, so you can just pick out the rest. On stage, or mid-jam, just knowing where to start a part is usually the leg up you need.
Next part: Yankee Doodle keep it up .... D string, first finger. That would be an open E string. After all, no finger is down from your index, and that's what you're playing the note with: no finger.
Q: Which is better, complete happiness or a ham sandwich?To burn in this idea of two-strings-down, one-finger-up, let's look at a couple of chords.
A: A ham sandwich, because nothing is better than complete happiness, and a ham sandwich is better than nothing.
Closed D? Index finger, E string; middle, D string. Ring, A string; pinky, G string. Rhymes.
Closed G? Index, D string. Middle, E string? Nope, that's not an octave. Must be a different note in the chord. Ring, D string. There's the rhyme with the middle finger. Pinky, G string. Doesn't rhyme with the ring finger, so a different note in the chord.
Now that you see this, race through every chord shape you know and look at where your fingers lie. You'll find it very gratifying.
Fiddlers, who are more intellectual than mandolin players and can read music and stuff, go this idea one further. When they play in D, they make the octave easier to find by tuning their G string up to an A. Any riff they play on the second string can be played on the fourth with the exact, same fingering. When they play in A, they also tune their D strings up to an E, so the fiddles, now tuned AEAE, let them finger tunes the same way low or high.
Sometimes, they'll tune the top two strings down, instead, to GDGD, to play G tunes. Either way, they don't have to think about the names of the strings, only "low" and "high."
These sawmill tunings won't work well on a mando, which is built for much higher string tensions. Tuned down to GDGD, your top strings are so loose the upper octave sounds weak. Tune up to AEAE and you'll rip your bridge off.
