When George Van Eps (1913-1998) came up with the idea in the late 1930s of adding a seventh string to his guitar, it allowed him to play a bass line along with his chords and lead solos.
Van Eps became a master of the seven-string instrument, which was adopted by only a few other jazz guitarists, among them Howard Alden (a former student of Van Eps). Late in Van Eps's career he and Alden recorded three duo albums for Concord.
Mellow Guitar was issued by Columbia in 1956, in mono only apparently. The recording featured three distinct settings for Van Eps's guitar: a basic rhythm section, a nine-piece band arranged by Paul Weston with whom the guitarist frequently worked, and a string orchestra. A link to a sample track (taken from the vinyl LP) is below.
What Is This Thing Called Love
Mellow Guitar was available for a short time on CD on the Sundazed label, which issued it in 1999. Copies now demand premium prices, $30 and up. The album is also available as a download, but it's from the British company Hallmark, which often uses vinyl as its source. The usual caution -- listen before buying -- applies.
Via YouTube, here's another selection from Mellow Guitar.