The Danelectro Longhorn Model 4623 was introduced in 1958. After a quick re-location of the treble pickup farther back on the body in 1959, the Longhorn basses survived through the 1960s with only minor alterations.
Were they a baritone electric guitar or a bass? There is no definitive answer, but you can certainly tell they are neither a bass or standard electric. Every studio has one or a Fender VI because of their unique sound.
In 2002 MTV reported:
And what instrument did Glen choose to use during the recording....a Danelectro Longhorn."STP bassist and songwriter Robert DeLeo has spoken in interviews about his love for the country-pop performed by Johnny Cash, Jimmy Webb and especially Campbell. And last year, Campbell's budding musician son Cal introduced his dad to the music of the Pilots. Soon after one of Campbell's Los Angeles shows, the band went backstage and met the legendary singer/songwriter. They all got along so well, Campbell invited DeLeo, his guitarist brother Dean and drummer Eric Kretz to record versions of classic cuts such as "Wichita Lineman" and "By the Time I Get to Phoenix" with him. They also worked on additional new material for Campbell and the band to record together, but by all accounts, their version of “Wichita Lineman” was the sole collaboration that was completed."