Best "one-on-one" recordings... one voice and...

... one instrument. I'll chime in with Ella Fitzgerald and Joe Pass on "Take Love Easy."
Excuse me, But even though I learned math in the Detroit public school system but I am pretty sure that Joe and Ella is 2

Eva Cassidy " Fields of Gold " Is one of my favorites
Jesse Colin Young, Soul Of A City Boy.
I mean one voice and one instrument.
This is the best I could find from my collection, and not true to the rules
of the thread, but excellent nonetheless...acoustic guitar and vocal (Lyle
Lovett) and electric guitar (Dean Parks) on "Promises" from
Lyle's "The Road to Ensenada" CD. Until I went to look up
the song title just now, I had always thought it was Lyle solo with
acoustic guitar.
Eva Cassidy - "Tall Trees In Georgia"
Greg Lake - "Lucky Man" and "Still You Turn Me On" from "Welcome Back My Friends To The Show That Never Ends"
I know this is an old post but I have been listening to Colin Haye for months and can't get it out of my head. He is the former singer from Men at Work in the 80's. I never cared for them then but this album is stuck on me. Just him and an acoustic guitar.
This is a slight cheat on the subject, but I find it an incredible recording:

Open Fire, Two Guitars - Johnny Mathis
Vincent Black Lightning - Richard Thompson
Joan Biaz - "Diamonds and Rust" (can't recall which old album this came from but this is definitely up there with the very best)
Diamonds and Rust is from "Diamonds and Rust" (A&M SP4527) released in 1975. However, this song is not a voice and single instrument recording. There is a full instrumental ensemble including an ARP synthesizer.
Is Michael Hedges just solo?, I know it sounds great
Philbrady - agree on the Colin Haye disc, it just stays and stays in my player sometimes, great songs, solid artist, good recording...