The Importance of Pinky
In the Planet Jazzmando, be prepared to use Pinky...

Much Folk, Most Celtic, and a hearty share of Fiddle tunings rely on the mandolin's open string structure, not only for that natural resonance, but the ease and facility in fingering the diatonic scale. Plus, the ability to "drone" beyond the keys of G, D, and A would require much more movement of the left hand fingers, so it's only natural that players in these styles would let there pinky get a little "dormant."

Not so in Jazz!

First of all, most of the great Jazz "Standards" are in "horn" keys--Eb, Bb, F, etc., all which take advantage of the overtone series these instrument are based on.

That means new demands on an instrument tuned in fifths--with four fingers only to six frets, you're going to have to use that pinky!

The ability to move up and down the fingerboard is critical to playing jazz. The sheer magnitude of "tonal centers" and key changes in most jazz literature demands an ability to abandon the first positions of the mandolin (1st finger 2nd fret, 2nd finger 4th fret, 3rd finger 6th) and rely much less on open strings,as you would in Bluegrass, Celtic, and other "Folk" music, that stays rigidly in one key, rarely straying into the realm of lush chromaticism in jazz.

I suggest it's easier to learn the "closed" position (NO open strings) first, and move your "home position" patterns, modes, up and down the frets FIRST, and learn to maximize the open strings later.

This REQUIRES a strong and flexible pinky finger, which is just plain unnatural! The way the hand is created with it's strong interdependence between the 3rd & 4th finger is a barrier that can be overcome, but not without exercises.

I propose a somewhat radical approach to learning modes and scales.

In first position, ABANDON THE OPEN STRING COMPLETELY AND USE YOUR 4TH FINGER ON THE SEVENTH FRET. I'm not saying you do this all the time, just when you're on the "pedagogy" part of your practice time.

If you devote your attention to this, you have immediate transposable shapes that can move easily up and down the frets, all four fingers working for you. This also helps a develop a tactile sense of scale degree function.

I use this approach to learning and practicing all my scales, warm up exercises, and even Fiddle Tunes.

It seems paradoxical to take this approach on Fiddle Tunes, since most of these were written SPECIFICALLY to capture the beauty and resonance of the open strings. But again, I'm only refering to this a PRACTICE routine, not something you do in performance. It's much easier to pick up the open strings later...

Observation:

Folk, Celtic, and Bluegrass Music are written around the open strings of the fretted instruments. Jazz uses more "closed" fingering, and uses open strings as a "bonus."

Loosely defined as music written in the late 19th century around a violin, or more accurately "fiddle," this music also enjoys the wealth and influence of other music that crossed the Atlantic Ocean, and wove itself into the American culture.

Largely based around the open tunings of the violin (also G,D,A,E), this collection of music provides a rich glimpse of early North American culture and its heavily European influence.

Many of these Fiddle tunes where incorporated (if not "evolved") into Bluegrass music, and popularized by Bill Monroe, who did much to define the role of the mandolin in the small ensemble, as a solo, accompaniment, and even a "Chop" rhythm instrument. But that's a topic for another discussion..

Fiddle tunes can be found in many published collections, including Fiddler's "Fakebooks." Because the tradition is largely aural, pockets of interpretation and variation exist, but learning these can be extremely valuable not only for "jams," but developing dexterity and technique.

As I mention in another section, Jazz tends to rely more on "closed" position fingering, yet practice on these tunes are not only fun, but facility builders. The jazzer would benefit from a more academic application by playing these with no open strings (subbing the 7th fret pinky for the next open string),but they can be a lot of fun to play the traditional way, too!

Look for them in the violin section of your favorite music store.

Profundity: Growth is when "practice" crosses the threshold into "discovery."

I recommend
Oak Publication's
"The Fiddler's Fakebook"
by David Brody.