"Moving" the Top
Subjective Concepts: Tone Production

The Sound Production Chain of a fretted string instrument goes something like this:

Strike string with pick making it vibrate.
Sound is pressed (transversed) through the bridge to put the top in motion.
Motion sends a column of air outside the holes which produces the tonal characteristics (pitch, volume, timbre) of the instrument.

We've already looked at the importance of keeping the pressure of the left-hand fingers on the string for maximum note duration (minimizing the gaps between notes). There's yet a "Big Picture" concept that might help you produce fuller, consistent, and more legato phrases, that of "Moving the Top."

I remember my college trombone teacher standing in front of me while I played, waiving his arms as if he were directing a garbage truck into an alley. "More Air! More Air," he'd scream. While I played, if he could hear the intensity start to diminish before the end of the phrase, he'd continue his admonition, "Air! Air!" After many months of working on this, I was able to produce fuller phrases with this sort of "visual," pushing the sound all the way through the horn, and not letting up until the end of the phrase.

Mandolinists can be guilty of losing the rich linear "line" aspect of playing by not consistently moving sound down the chain of string, bridge, top, and chamber.

Think in terms of not only of keeping the string going, but "moving" or vibrating the TOP of the mandolin. This larger goal gives virtual "breath" to playing flowing, melodic lines.

Thoughts on Jazz Tremolo:

In my never-to-be-humble opinion, dependency on a thick tremolo is the wrong answer to sustain! (At times, it's downright cheap, and has irrefutably given the mandolin a bad name...) Keep in mind, every time the pick strikes the string, it's also momentarily choking the vibration. If your approach is to keep the TOP of the mandolin moving, even tremolos will be fuller. It might even help you conceptualize better articulations with the right hand, making you relax the wrist more. Though a firm pressure from the left hand is necessary, you still want to maintain a relaxed wrist and forearm in both hands. Isolating undue attention to just "lock" gripping the string would be averted, if your attention is on the sound coming off the top of the mandolin. Use the ears as your gauge--if the sound is diminishing prematurely, you will sense the need for correction!

Now, go move some wood!

Bonus! Here's a great exercise PDF for developing left hand finger control:
  Guides and Gravity