I’m talking about the five-note harmonica or guitar line that repeats over and over. It goes A-D-A-C-A (A being the lowest note), followed by a rest. Here are a couple examples:
Mannish Boy: http://www.youtube.com/watch?v=Ekoh2HJAwBk&feature=related
Bad to the Bone: http://www.youtube.com/watch?v=UYPcY15JaWY
AFAIK there’s no name for it – it’s just the Mannish Boy riff. There’s a lot of 'em like the “Lonely Avenue” riff or the “Boogie Chillen” riff, just part of the language, which don’t really have names officially in my experience.
Never knew a name for it, but if you sing a rough 1-second sample to any good musician, he will instantly know what you’re talking about.
It’s just a I-III-IV riff, is all. There’s lots of them.
I always called it the “Woke up this morning” riff. As in:
“I woke up this morning…”
Duh-DA-Duh-DA-Duh
“…my baby was gone…”
Duh-DA-Duh-DA-Duh
But that’s just my personal way of thinking of it. Never heard a formal name for it.
That’s what I’ve heard it as.
It’s the Chanel No. 5 of riffs. It’s the one everybody knows, but at its base is nothing more than just another blues riff, one of many.
Funny that you should pick those two examples. There is a woman at work who has that riff as her ringtone. One day her phone was ringing and ringing while she was away from her desk. Almost simultaneously, I started singing “I’m a man… spelled M…” while the guy in the cube next to me started singing “Bad to the bone…”
The I-III-IV is good, but’s bugging me as a keyboardist – maybe I7 - IV7 - im7/iii - I7? Just don’t ask for the keyboard tab, it’s beyond my skills 
My experience with keyboardists has been that often what are standard conventions on guitar don’t always translate well to keys.
A friend of mine, a very talented keyboard player and composer, was bitching to me once about how he could literally do nothing with the Pentatonic scale on piano. I picked up my guitar and played nothing but Pentatonic noodling for the next 40 minutes while we talked. He was livid.
Even better would have been if you’d picked up Chick Corea or McCoy Tyner, had THEM pick up his piano, and asked them (nicely, and probably with the inducement of some big paper) to play pentatonics for 40 minutes.
It’s good to hear some turn-about back on the piano pickers for a change – seems we’re always griping about everybody else, only seems fair to hear from the other side of the guitar pick for once. Just nothing in B major okay? 
No worries, I’m a fan of A#/B flat minor myself. Never was much of a fan of B Major.
Sounds like he wasn’t familiar with the rock or country idiom, then. Pentatonic major or minor (5-note blues scale) are standard rock, country, and blues scales, and any keyboardist worth his salt who can improvise in these idioms should have no problem with pentatonic noodling.
It does get a bit boring, though. While I can endlessly noodle on the pentatonic, I often will throw in passing tones, and occasional outside notes in it for variety’s sake. (For example, if I’m soloing a pentatonic major in country, I’ll throw in minor third grace notes in there every so often. Us keyboardists can’t bend notes, so that’s the best we got.)
And the “Mannish Boy” riff is all over the I chord. There’s no III or IV in there.
I hear John Lee Hooker in my head when I hear that riff.
I’ve been playing some Bob Wills covers for fun (and small bills) recently – all that Western Swing is pretty strictly (no pun intended, but incidentally Al Stricklin plays a bunch of piano on a lot of the classic recordings) pentatonic when soloing, at least in that piano style. I guess the point was more that those patterns fit more “in the box” for guitar, which was why it was such a big deal for later (jazz) pianists to start using the same quartal chords and pentatonic scales (plus passing tones and chromaticism) that (at least for the chords) were always in the bag more or less as options for guitar players. I don’t doubt the guy was a monster player – I’m pretty OK on organ and piano, reasonably big repertoire, reasonably experienced, all that, but I can’t tear off some Woody Shaw-style lines all that comfortably on piano compared with people who practice that style. Ray Charles couldn’t, either, or else he probably would have, right? 
I was fretting about that little roman numeral “analysis” also – probably best put a nice big “N.C.” over the riff and call it a day, but didn’t what Otis Spann and everybody hits on the do-FA-ri-do thing at least for the IV7 chord? Not that it really matters, but I know I’d hit the IV7 as a chord at least partially – sounds good like that anyway. I’m always confused about how to notate blues anyway – I do questionable stuff like try to spell the blue third like a sharp nine for no good reason other than obsessiveness. Nothing matters but the sound, but I think a lot of musicians have a little ADD in them, including me.
I dunno. I usually hear this riff either as single notes or fourths/fifths.
Yeah, sometimes, sharp nines are spelled out, but in blues, I leave them out. Using the terminology of classical harmony to notate blues/pop/rock music can lead to unnecessary complication and obfuscation, IMHO. And not every note in a bar is a chord tone, anyway.
At any rate, the deal with the pentatonic scales is that when I was learning improvisation, that was the first thing taught to me. Granted, I was learning to improvise in pop/rock/country/blues styles, but those are usually (from what I’ve seen) the first scales taught to any musician wanting to gain improvisational skill in these genres. It’s not somehow limited to guitar, although guitarists are more apt to learn it quickly, because guitarists are more likely to start learning in these genres vs. piano players/keyboardists, who have a tendency to go the classical route.
There is a name for that style of accompaniment: Stop-time.
I think you’re overthinking it. Blues relies heavily on fourth patterns. This is just i-iv-(iii)-i (The minor is just a carry-over from the key–it’s usually unison/octaves or fifths.) For this to be a i-iii-i pattern, the D would have to be removed. This is a variation.
Another variation I’m familiar with uses a either a ♭VII or i[sup]11[/sup]. In the notation in the OP, the melody would be GCGCA, with the G being lower than the A.
ETA: And no, it’s not that hard to do classical analysis on blues–you just have to remember that not all tones are supposed to be harmonic.
It’s not a i-iv-(iii)-i progression. You would never play it as em-am-em-gm-em. If you want to play all chord tones, you’d play it as E-A-E-G-A. But I would still consider that riff all over the I as it is usually played.
Which is what I mention in my post. Yes, you can analyze blues through the classical tradition but, as I also mention in my post, I think it can lead to confusion; blues melody and harmony doesn’t neatly fit into Western classical music tradition. For example, I have never seen blues analyzed as having minor harmonies, except in the special case of minor blues. It’s almost always analyzed as I7, IV7, and V7.
The one stopping point for me in harmonic analysis is that dominant seventh on the tonic – in strict major-minor functional harmony, this could never be the basis for a tonality, as it is in the average blues tune. As far as I know, anyway, which may not be much. Maybe theory would avoid this by calling the I chord not a 7 chord, but a major chord with the b7 included as an appoggiatura leading down a half step to the fifth degree of the IV7 chord?
Melodic things like solos would seem to be pretty straightforward to “explain” using the kind of analysis jazz people, for example, perform sometimes on transcribed solos. Tension, release, major, minor, blues pentatonic scales, chromatic passing tones, that sort of thing.
Not where my head is at, but somebody’s probably got a book out there of that kind of thing.