While recording his "Beyond Nature" album, Phil Keaggy spent many hours doing three things -- playing acoustic guitar, taking long walks in the woods and reading books by C.S. "Jack" Lewis.

"I took all that in and it influenced the music, which was quiet and contemplative and that fit with that moment in my life," said Keaggy, in a recent interview. "All of that was connected. … I think you can feel a spirit behind that music."

So it isn't surprising that this 1991 classic included song titles such as "Brother Jack," "Fragile Forest" and "Addison's Walk," referring to a Magdalen College footpath that Lewis, J.R.R. Tolkien and Oxford friends often walked while discussing literature, faith and life.

While "Beyond Nature" was an instrumental recording, the liner notes included this Lewis quote: "Nature is mortal; we shall out-live her. … Nature is only the image, the symbol; but it is the symbol Scripture invites me to use. We are summoned to pass in through Nature, beyond her, into that splendor which she fitfully reflects. And in there, and beyond Nature, we shall eat of the tree of life."

So this was a "Christian" album, one inspired by the apologetics of Lewis? That's the kind of question musicians often hear after recording instrumental music during an era in which "Christian music" debates almost always focus on lyrics.

"I just play," said Keaggy. "I don't try to analyze all that."

In recent years, Keaggy has recorded a series of instrumental albums with keyboardist Jeff Johnson, who -- like the guitarist -- has for decades mixed folk, rock, jazz, classical and Celtic music into a style that writers struggle to label. Both record most of their music in home studios on their own terms. Both draw the attention of critics outside the "contemporary Christian music" niche.

The duo's latest work, for Johnson's Ark label, is "Cappadocia" -- taking its name from an arid, volcanic region in what is now Turkey. Early Christians hid in this isolated haven during persecutions and the Apostle Peter addressed his first epistle to "exiles" in several places, including Cappadocia.

Johnson visited this region in 2017 and was stuck by remnants of Christian life, from pieces of frescos and engravings to a rose-shaped window in a sanctuary carved into a hillside. Thus, the disc includes song titles like "Chapel of Stone," "Parousia (A Presence)" and "That Which is Hidden."