This topic is near and dear, so I'll hope you'll forgive me if i wax a bit autobiographical.
There were five artists that informed my early and therefore formative tastes(earliest influences strike me as truly foundational, kinda like your first serious girlfriend). Three of them I'm sure no one else has ever heard of; the fourth you might know if you're a guitar fanatic; the fifth is familiar to some serious classical fans.
1. Joe Brice
2 & 3. Schubert and Ruth Parkinson
4. George Van Eps
5. Dennis Brain
The first three are all from my hometown, which, at that time, was a thriving metropolis of about 6000 souls. Joe was a real world Mr. Holland, and his magnum opus was his students. I wonder how many other music teachers produced three Tonight Show band stalwarts (remember, in the 60's and 70's that was the best big band gig there was) and at least 8 musicians (there may have been more) to graduate from Julliard from such a miniscule pool of potential talent? Schubert and Ruth owned the only Steinway dealership for hundreds of miles, and, with their three children, had a fine woodwind quintet that traveled the country and often performed with the smaller regional symphonies. They were a second family to me; I worked in a desultory fashion in their store from the age of ten until I left for college.
They're all gone now, but they shaped my musical tastes and began my musical education. Dona nobis pacem.
It was in fact Brice who suggested and the Parkinson's who helped me obtain the first record I ever bought---Dennis Brain's recording of the four Mozart Horn Concerti and it seems to me miraculous it has survived wives, girlfriends, dogs, cats, a disastrous fire, a peripatetic life and a checkered career. I own it still. And to this day I believe it's the nearest thing to a perfect performance I've ever heard.
Van Eps was my own discovery. At age 13 I got a copy of his "Mellow Guitar" (unfortunate title) and shortly thereafter began to teach myself a new way of playing guitar--an instrument Van Eps like to call a "lap piano." To this very moment his 7 string "They Can't Take That Away from Me" has the power to transport me.
Grumpy's signature quotes Ellington--there's only two kinds of music: good and bad. I concur with Ellington.
The fact that today I listen to all manner of music is testament to these little known artists, They are the ones who taught me to see the difference between good music and bad.