Riffs are the backbone to rock music, monstrous in their ability to captivate us. They can propel a song into iconic stadium territory. And once you have learnt and mastered classics like Smoke on the Water and Back in Black, it is only natural to think about writing your own. The great news is that, given their simplicity, creating great riffs is no more difficult than playing them.
KEEP IT SIMPLE
First things first, there is no set formula to creating riffs. Inspiration can strike at unexpected times - if you try and sit down to write one, nothing may happen. Tom Morello of Rage Against the Machine came up with Killing in the Name while teaching a student about Drop D tuning, before running off to grab a tape recorder. Riffs have no limits unless you impose them, and generally range from one to four bars in length.
But there are some guidelines to help riff writers. Keep in mind the KISS principle ("keep it simple, stupid"). The basic and repetitive nature of most well-known riffs means that, even if you have just touched up a guitar, they can be picked up in little time. Don't worry about being a technical genius or knowing countless scales (knowing the E minor pentatonic may be a good idea, however) as most riffs are composed of a few notes and tend to follow the same patterns.
If I had to sum up what makes a killer riff in five words it would be as follows - rhythmically compelling but basic melodically. Satisfaction by the Rolling Stones has just three notes, and Led Zeppelin's Immigrant Song has two (one discounting the octave). Hooks should do exactly that - grab the listener's attention, much like the choruses on top forty radio. Try to make it instantly appealing - will a ridiculously overblown section will not stick in your head or get you off your seat at a concert? There are a few exceptions, like Metallica's Master of Puppets, but basic is generally best.
LEARN FROM THE BEST
It may be a cliche, but to be the best, learn from the best. And to write great riffs, listening to great riffs for inspiration is a great idea.
Take the instantly recognisable introduction to the Guns N' Roses song Sweet Child o' Mine, which Slash first played as a joke as a "string skipping" exercise. The same goes for Nirvana's Smells Like Teen Spirit, which uses just four power chords, all in the same shape. Kurt Cobain himself called the riff "cliched" and Krist Novoselic initially dismissed it as "ridiculous," but its simplicity has made it a classic. The notes just work perfectly together.
Californication by Red Hot Chilli Peppers is little more than two arpeggiated chords (A Minor and F), further evidence that if you think a riff idea if too easy to play, it almost certain isn't - you may just have struck gold.
But make sure your riff is not overly repetitive. As playing the same notes throughout an entire song will not enthral a listener, creating some variation is vital. Perhaps use mostly chords for the verses, like with Jimi Hendrix's Purple Haze, or vice-versa (Fire).
How about playing the riff in different keys (Are You Gonna Go My Way? by Lenny Kravitz), or having various memorable riff that repeat throughout? In many Led Zeppelin songs, like Black Dog and Moby Dick, just when one riff seems to be going on for too long, it switches to a different root note. Such a change is very effective.
Smoke on the Water by Deep Purple opens with the classic riff, before being doubled on an organ, and joined by drums, bass and vocals. In the introduction The Beatles' Day Tripper, the riff is played once on its own, then along with the bass, then a tambourine joins, before finally a drum kit and John Lennon's vocal. It is also played slightly differently during the verses as not to be too same-y.
Experiment with the structure of your riffs. Try out the 3+1 structure, commonly associated with Metallica. A one-bar riff repeated is three times, but the fourth bar is a new phrase rounding off the riff well - before it all repeats. Arctic Monkeys recently used a similar technique on their single Don't Sit Down 'Cause I've Moved Your Chair. Maybe use power chord combos.
GOOD ARTISTS BORROW...
As the infamous quote goes, "Good artists borrow, great artists steal." And seeing as virtually every of a riff has already been created, don't be afraid to copy some ideas from other artists. Everyone has done it. The Beatles? Check. Led Zeppelin? Check. Even Hendrix mentioned stealing a couple of blues licks here and there.
The other day, I came up with a great riff while improvising. But when I looked back over it, I realised many of the notes were similar to songs like Day Tripper, Moby Dick and probably many others. I had not listened to either song for weeks and the riff sounded nothing like them - it was a completely different pattern played at a different tempo - but it just shows that is neigh on impossible to come up with something completely original.
You may also experience cryptomnesia (subconscious plagiarising someone else's work), as Paul McCartney did when the melody to The Beatles' Yesterday came to him in a dream. When you come up with something, like with my riff (even most people would not pick up the similar notes), it is possible to think, like McCartney, "Has this been done by someone else?" If you can't instantly recall the riff, the chances are you haven't ripped it off and won't be sued!
What I'm trying to say is that your influences will always shine through, which is why they should be as broad as possible. Try to expand the variety of music you listen to - look at how Hendrix incorporated so many genres, including jazz and soul, into his brand of rock. It will make you a better and more unique player; have your own style, rather than just trying to imitate one guitarist.
I don't advise stealing entire riffs (which huge bands such as Oasis and Led Zeppelin have admitted to regularly doing), but don't be ashamed of your influences. Maybe take a riff and turn it on its head, changing the pattern, phrasing and notes, like I unintentionally did with my Moby Dick/Day Tripper-esque riff. Give it your own twist, adding vibrato or bends.
Good luck with your riff writing! Remember to keep it simple but not boring - variation is vital. Listen to the legends and don't be afraid to sneakily borrow some ideas from them. To round off, I advise you to come up with as many riffs you can; not all will stick, but working on many will increase the chances of one working in a song.