The songs Layla and Skateaway came on the radio yesterday evening. My wife commented that in both songs – at least the studio versions – Duane Allman and Mark Knopfler, respectively, are playing country/western-style slide guitars.
I’m inclined to doubt this, but I bring the question to the informed body of musical Dopers – is my wife correct?
Duane is definitely playing on Layla - as he plays all through the alubum. After all, the “Derek” of “Derek and the Dominoes” is Duane and Eric.
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And inasmuch as “Skateaway” is on the Dire Straits album “Making Movies,” yes, Mark Knopfler is playing on that.
Maybe I don’t understand your question. When you say “country/western style slide guitar,” do you mean dobro? If that’s your question, then, no - I don’t think it’s a dobro even in the last part of “Layla” (the part anchored by the Bobby Whitlock piano). I’m not sure about Skateaway. Knopfler plays the occasional dobro - or at least the occasional National guitar.
I think the question is about the musical instruments, not about the identities of the players. 
Slide guitar is a common technique not just in country but in blues and rock as well (e.g. Bonnie Raitt). I think maybe the OP is thinking of the pedal steel guitar, a much more specific instrument played with a slide, whose twanging sound is commonly associated with country (and Hawaiian) music.
Here’s a page that explains the diffences between playing a regular guitar with a slide, a steel guitar, a Dobro, and a pedal steel guitar:
http://www.guitar.com/columns/viewcolumn.asp?columnID=58
No doubt a guitarist will chime in with the Straight Dope, but my non-musician’s opinion is that Duane is playing a regular guitar with a slide on Layla, not a pedal steel.
Yes, that’s exactly the instrument I was thinking about – a pedal steel guitar. I’ve always called it a “slide guitar” and no one has ever corrected me <shrug>.
I was pretty sure that Allman didn’t close out Layla on a pedal steel guitar. I don’t think my wife is right about Knopfler’s work on Skateaway, either. Playing with a slide over a finger seems to be what’s happening on those two songs.
One of Duane Allman’s “trademark” bits was to use a slide on a standard-tuned electric guitar. In the “Allman Brothers Band” days he was often pictured playing this way on a Les Paul. His common technique was to use a pill bottle for a slide on his little finger, alternating with fingering with the other three fingers.
Knopfler often plays a Dobro, or more generically, a resonator guitar (Dobro is a tradename - National is another well known brand of resonator). He uses more-or-less traditional tunings and techniques when playing it, as far as I know. In fact, I think Knopfler favors a National he owns.
I’ve never heard of either of them playing a pedal steel.
A famous rock guitarist who DID play pedal steel a lot was Jerry Garcia - he played pedal steel on “American Beauty” and on one of his Solo efforts, as well as with “New Riders of the Purple Sage” when they toured with the Dead, and on their first album. He also played pedal steel on “Teach Your Children” from Crosby, Stills, Nash and Young’s “Deja Vu” album.
In fact, here’s a picture of the 1939 National O body “Duolian” model that Knopfler uses:
http://www.planetmark.org/guitares/guitare15.htm
You might also recognize it from the artwork on “Brothers in Arms”.
Back in 1983 or so, Guitar Player magazine did an issue commemorating Duane Allman. Somewhere in the mag, it was mentioned that Duane played the screaming solo done to the chorus riff, and Eric Clapton played the singing solo over the piano. I think but I’m not sure that Allman said this in an interview that was reprinted in the issue.
[TANGENT]Duane Allman used a Coricidin bottle as a slide. Coricidin supposedly used be an over the counter cough medicine with a small amount of codiene mixed in. Supposedly, it was popular with coughing blues musicians.[/TANGENT]
In the histories that I have read, Allman was supposed to be playing his Les Paul up past the neck to get those super-high, soaring notes during the Jim Gordon-penned piano close to Layla (IIRC, the main song and the piano break - I think the guy’s name was Jim Gordon, he was the drummer - were not written together, are obviously in different keys and were combined in the studio. Later Gordon was diagnosed as mentally ill and ended up killing somebody with a hammer or something…
ANYWAY (sorry for the diversion) Allman going above the neck to get the high tones was a big deal - a new take on slide…and definitely on a standard guitar, not a pedal steel…
Jerry also played pedal steel on “One Toke Over the Line,” by Brewer and Shipley (a one hit wonder band if ever there was one).