I don't think I had even heard Ralph Towner's name when I saw Blue Sun in a record store sometime back in the 1980s and bought it on the strength of the cover art. I don't know how well you can make out the photograph that occupies the center of it, but it's a very beautiful sea and sky picture that makes me think of a Scandinavian summer.
Image swiped from the great ECM fan site between sound and space
Not everything on the album lived up to the promise of that image, but enough of it did that I didn't regret the purchase, and have bought two other Towner albums over the years. Most of his work is on the wonderful ECM label, and I've learned since that I can pretty well rely on finding anything issued on it at least interesting.
Towner's music occupies a sort of indeterminate territory which comes out of what could broadly be considered a jazz culture or sensibility, but is not exactly jazz, and not exactly anything else, either. It could be called ECM territory, as a lot of the label's output fits there.
From Solstice, which I don't have, but which Allmusic.com says is his best album, and so worth investigating, here is "Nimbus":
From Ana, "The Reluctant Bride" and "Green and Golden":
I don't know of anyone else in the world who can play a 12-string like this. "Spirit Lake" can be found on Solo Concert, but this is a different and even more spectacular performance.