I've always used all of my fingers when I play, but lately I've been experimenting with more single and double-string runs up and down the neck instead of across the strings. When visiting Turkey, I noticed much of this type of playing on instruments with less courses (saz, baglama, trichordo). The key to this, for me, is using the index and middle fingers almost exclusively.
This evolved into me also experimenting with two-finger playing in the familiar scale and arpeggio patterns, across strings in diagonal patterns.
The result is fresh phrasing, better vibrato, and a more balanced hand. Trying to figure out how to get from point A to point B with only two fingers encourages chromaticism, glissando and frees up the horizontal/diagonal movement of the fretting hand considerably. I also seem to have more "punch" now.
I'm now using the index and middle for 75% of my single-note playing, with the ring finger and pinky playing 20% and 5% respectively. I've come to think of the pinky as a "dead-end".
It just feels so much better to play this way and I'm surprised that it really doesn't slow me down and, in some cases, even increases speed.
Has anyone else experienced this revelation?