On the Beach - tuba tone

[Oric]

first of all, On the Beach is one of Neil's best solo albums. Raw as hell. I'm especially digging Levon Helm and Rick Danko on Revolution Blues. When I first heard the song, I swore it was a tuba playing the bassline (and I'm a tuba player, so I know what a tuba sounds like). But nope, just Rick Danko. That man can play bass. It sounds like a fretless, his Ampeg AUB-1. What kind of settings does he use to get such a bangin' tone?