When Red Dog speaks, people listen.

No, not Clifford the Big Red Dog – although a 25-foot-tall mongrel does demand attention. This Red Dog is blues guitar legend Elvin Bishop’s beloved cherry red 1959 Gibson ES series six-string, a guitar that’s served him since 1962 or ’63.

Red Dog was at Bishop’s side when he helped take blues to white American audiences as a member of the Paul Butterfield Blues Band, trading licks with Mike Bloomfield on the band’s epochal eponymous debut and the evolutionary East-West. And the durable beast served him well during his days as a mid-’70s hit maker, on the Southern rock gem “Struttin’ My Stuff” and the No. 3 smash “Fooled Around and Fell in Love.” When Bishop returned to the stage and studio in 2005 after a lengthy absence, the ever-faithful ES-345 was with him once again.

Today the road-worn but elegant six-string still sits in Bishop’s lap – at least when he’s making a new album or on a driving gig.

“A friend of mine looked up what Red Dog was worth and it scared me so much I stopped carrying it on airplanes, since the airlines would only give me about $400 if they lost it,” the 67-year-old string plucker and singer explains.

Except for dings, scratches, stickers and scuffs, Bishop’s ES-345 is as stock as it was when he got the guitar from fellow Chicago blues legend Louis Myers. If anything, like great vintage instruments tend to, it may sound better with age.

To get an earful of this special guitar’s powerful voice and the rapport Bishop has established with his primary instrument over 40 years, check out Bishop’s new Red Dog Speaks. The album is part house party, part pickin’ party – thanks to guest turns from west coast guitarist Tommy Castro, Oakland soul singer John Nemeth and Louisiana zydeco legend Stanley “Buckwheat” Dural, and part musical autobiography, with Bishop telling stories about good times (“Fat and Sassy,” “Blues Cruise”) and hard times (“Midnight Hour Blues”).

Occasionally the narrator is Red Dog, who, with Bishop’s guidance, does indeed speak. And some of the Dog’s most eloquent narratives are on slide – clean and keening on the instrumental version of the gospel number “His Eye Is On The Sparrow,” barking and howling in the dirty title track and parlaying a tone warm and age-soaked enough to turn back time on Bishop’s “Doo-Wop Medley.”

What’s truly spectacular about the tone Bishop conjures up on his classic ES-345 is the way it seems to compress the development of blues and other electric American music from the late 1940s through the mid-1960s into its grizzled-yet-sensual sound. At its best, Bishop and Red Dog’s interplay is elemental and transporting.

We spoke to Bishop recently, to get the low-down on his historic instrument.

How did you acquire Red Dog?

Well, I’m not too proud of this story, but here goes.

I was playing a place called Big John’s on the north side of Chicago in the early ’60s. It was the first place that allowed us to play blues for white people. It was a hell of a thing, because at that time you played from 9 p.m. until 4 a.m. – and until 5 a.m. on Saturdays – 45 minutes on and 15 minutes off.

The first thing we’d do on a gig is make friends with the bartender. The clubs would give us beer for free, but charge us for hard liquor. If the bartender liked us, we’d get liquor free. We used to drink these things called “Polish Martinis” – a double shot of gin in the bottom of a beer mug. The boss man would come by and say, “How are these guys getting so tore up on beer?”

Well, I had a Telecaster that kept breaking strings. It had a bad problem. And I told Louis Myers, a great guitar player who played with the Four Aces, a band that backed up Little Walter and Junior Wells, one night when we were drinking these “Polish Martinis” that there was something wrong with this guitar.

He said, “There’s nothing wrong with the guitar. You’re hittin’ it too hard. If I had that guitar I wouldn’t break a string.”

I said, “Oh, I bet you would.” He opened up his case and he had an ES-345 inside, and he said, “I’ll trade guitars and I’ll bet I won’t break a damn string.”

I didn’t feel like I had much to lose, so we traded, and over the course of that week I fell in love with the guitar. The sound was great; it felt so good in my hands. I loved it!

He came back the next week and said, “Man, every time I look at that Telecaster – ‘boing’ – there goes another string. I want to trade back.”

I said, “Sorry, man. I love this guitar. I can’t trade back. And that’s how I ended up with Red Dog.”

Your slide playing always sounds great – really nasty and sweet and old school. How do you approach slide?

I play slide in standard tuning nine times out of 10. I took my influence from Earl Hooker. I had seen him play slide and then switch to lead with just his fingers and decided I wanted to play like that.

When I started out we didn’t have guitar techs and you were lucky to have one guitar – nobody had two or three. So if you wanted to play in a different tuning for slide you would have to stop the show and tune your guitar up. I also use the slide on my little finger to leave the other fingers to pick strings.

I saw Hooker in clubs several times, and they were highlights of my life. He learned from Robert Nighthawk and took it to another place. Robert Nighthawk was very hard-core Delta blues. He played a lot like human voices. He would play melodies just like a singer.

I saw him once in Pepper’s Lounge in Chicago. He came into the club and didn’t even take off his coat. He jumped on stage and the guitar player who was there just handed Hooker his guitar. And Hooker immediately started playing variation after variation on “What’d I Say?” by Ray Charles. People were screaming and I swear it lasted for something like 45 minutes and if you closed your eyes you could hear Ray Charles singing.

That was all in standard tuning. Guys who play in open E tend to sound like Elmore James or Duane Allman. The only guy who has transcended that is Derek Trucks, who might be the guitar player of this generation.

If you play in open G it’s going to sound like Robert Johnson. It’s pretty hard to get past that. Tunings have ruined as many guitar players as Little Walter did harmonica players.

Blues can be, by structure, fairly simple and yet it’s extremely hard to play well – with real conviction and heart, as you do. Why is that?

The thing is, blues ain’t football. You don’t have to retire at 30. You can grow and play all your life. If you stay in decent shape you can keep improving. It just requires a bit of technique. Most blues players have too much technique. But what really makes blues sound good is how the pieces fall together in your mind. The older you get, the better you get at that.

What makes Red Dog so special?

They called it “the Gibson Stereo guitar” at the time, and this is just a great guitar. In the old days things weren’t so mass-produced, so every guitar from that year did not sound the same. In the old days the pickups had more windings and it wasn’t necessarily a standard amount of windings, and God only knows if the tropical wood the guitar [is made] from is extinct by now.

I’ve never heard another guitar that sounds exactly like it, so I’ve always left it the way it came. If it ain’t broke, don’t fix it. And if I’ve found any shortcomings, they were always more in me than the instrument, so I figured I’d better practice instead of complaining about the guitar.