“Riff” is a term of uncertain origin and very loose usage. The theory that it’s an abbreviation of “refrain” (as part of a song) is plausible, given that repetition is the premise and in some sense the goal of riffing. I’d like to tighten up the definition so that we can focus on a distinctive major asset a rock song can have. A riff, I submit, is a much-repeated motif dominating a song’s rhythm and bass parts that also has significant melodic interest, so that there’s a kind of short-circuit surprising charge to it as these diverse song-values come together. It feels like The Very Principle of The Song thrust unexpectedly in your face, repeating every four beats (“You Really Got Me”) or taking eight beats (“Satisfaction”)–long enough to be of melodic interest and short enough to be powerfully repetitive. Unlike various sorts of strong motif that are allotted their particular moments, the true riff carries large portions of the song, including verses. (“Purple Haze,” no; “Whole Lotta Love,” yes.)
A riff can strike us as pleasingly Simple, as in all the examples I’ve given so far, or as impressively Advanced. For me, as for many guitar and bass beginners through the years, the original Advanced Riff is in “Day Tripper”(The Beatles, 1965).
It’s hugely satisfying to play that figure once, twice, endlessly, and to meet the coordination challenge of singing the song over it.
A proper riff is a signature statement and a sturdy mobile platform – like a locomotive that will pull your train however long you want it to. “Sweet Home Alabama,” possibly the gold standard of radio-ready riffing, goes on almost five minutes, and you may not be averse to hearing it again.
Speaking of radio, the most consistently interesting band for riffs may be Radiohead. Surprising in retrospect, they did not start out living by the riff. They’re not doing it yet on Pablo Honey (1993) or The Bends (1995). In the last track on The Bends, “Street Spirit,” we hear a familiar device closely akin to riffing–the repeated articulation of a chord that lodges in your mind as a main physiognomic feature of the song. But that figure isn’t vying for melodic status or grabbing at the beats the way a riff does.
With OK Computer (1997) we’re suddenly in a different world in many ways, including riffwise. “Airbag” hits us right off with a blaring motif with great riff potential –
although no, that motif won’t actually be used as a riff. It’s Track 2, “Paranoid Android,” that defines the mature Radiohead approach and is built on a beautifully phased-in riff sounding at first like this:
Which turns out to be a teasing anticipation of the loud version:
A few tracks later, “Electioneering” gives you a robust riff possibility as an opening statement and then constantly reminds you of it, barely keeping a lid on it, during the verse – making it a Latent Riff:
Radiohead amazed the world with their next move after OK Computer, the electronica-oriented Kid A (2000). Listen to the spooky opener, “Everything In Its Right Place”:
It’s a riff! An interestingly borderline riff, just barely melodic and rhythm-accenting enough to qualify. Throughout Kid A Radiohead plays with the subtle difference between riff and background pattern, between vaguely melodic propulsion and submelodic texture. With many of these tracks, depending on your mood you can feel either the strongarming of a riff or the sliding-by of a pattern (e.g. in “In Limbo,” aptly named for my point):
“National Anthem” is a boldly riff-driven number where the riff is obviously a bass line first picked out on a guitar but then played as though it were an electronic loop in a process piece. A nice touch: as “National Anthem” transitions into the horn frenzy of its last half, the first horn we hear is a traditional honking saxophone reminding us of the grand heritage of riffing:
“Pyramid Song” (Amnesiac, 2001) offers a slow-motion piano-chord riff that is nothing like guitar-bass rock riffing–until after two minutes the bass finally comes in to prove that all along this has been precisely a dreamy revisit of “Satisfaction”:
Once you latch on to the riff, your experience of the song fundamentally changes. A train engine is taking you someplace.
“Go To Sleep” (Hail to the Thief, 2003) begins with a deceptively folky guitar pattern, something on the order of “You’ve Got To Hide Your Love Away”:
Quickly enough, you can tell it’s a riff. It declares its riffing nature even while confounding your perception of its time-structure (it’s in 10 in the first section, till 1:23 in the song).
Once it settles down to measures of 4, they show you the pure motor in it:
At the end the fade-out gently confirms your hunch that the same motor has been the essence of the riff throughout.
“Bodysnatchers” (In Rainbows, 2007) starts out very much in “Day Tripper” mode, stating the riff and then singing over it:
Then a chorus gets layered over the riff feel (the riff’s melodic part drops out but is still implied by the continuing percussion pattern), so you get the relentless reliability and the chorus’s enlivening change all together.
Will Radiohead ever quit riffing? The evidence of their last album is that they will not. You can’t tell at first; the opening tracks of King of Limbs (2011), “Bloom” and “Morning Mr. Magpie,” have patterns, not riffs (do you agree?):
But the riff is back in track 3, “Little By Little.” (Do you agree? This is an extraordinarily long one, four measures.)
In my estimation, Radiohead’s riffing train is still rolling.
As reverent students of the riff we should not leave our subject without saluting a prime historical source and overflowing fountain of riffing, the Count Basie Orchestra. Their riff mania starts at 2:08 in this youtube for “One O’Clock Jump.” It raises the question, can rockers go polyphonic with their riffing? Can riffs be layered and braided Count Basie-style? Or does that defeat the take-charge purpose of a rock riff?
Listen to Stevie Wonder getting a similar effect in “Superstition”:
 The expression “riffing on,” such as might be done by a comedian, implies an idea being used as a base for a series of forays, but now the “riffs” are the forays rather than the base. In music, riffing is what maintains the base.