This is a rant about a pet peeve of mine. Namely, the "sus4" chord - as in, "Dsus4". This is a completely wrong nomenclature and even major publishers are perpetuating the ignorance and confusion - I see it everywhere. Here's a grab of a "Dsus4" taken from a random "teaching" website - I won't say which one, just google "Dsus4" and this is what you'll most commonly get:
Let's break down the nomenclature. "Sus" means "suspended". When something is suspended it's raised. So "Dsus4" would mean that the 4th of a D major chord is raised. But that is not the chord that we see pictured. What we see pictured is (from low to high or from left to right for those of you who don't play guitar); root-5th-root-4th. That is not a suspended 4th, it's a 4th. In fact, what has been raised (suspended) is the 3rd. There is a half-step between the 3rd and the 4th so if you suspend the 3rd - well, that's the same thing as the 4th. However, there is a conceptual difference between a #3 and a 4th. The "D" means "D major". That's a triad; root-3rd-5th. The word, "suspended" or the abbreviation, "sus" when applied to a major triad means that the 3rd is sharped/raised/suspended. The diagram above is picturing a Dsus, not a Dsus4.
Dsus4 is a completely different animal: "D" = a D major triad: D (root) F# (3rd) A (5th). A suspended 4th would be a G#. So Dsus4 would be spelled D-F#-G#-A. Good luck with that. Piano? No problem. Guitar? Problematic. On the guitar, some kind of open voicing is the only way to play it, unless you're Allan Holdsworth. Here's my take on it:
Put the Root on the 10th fret and that would be one way to play Dsus4. Here's an Allan Holdsworth-type voicing:
I can actually play this one because the root is the open D-string:
Ouch and Ow! Holdsworth would probably do the physically impossible by putting the root on the 4th string at the 12th fret:
Now...when you see Dsus4 in a 3-chord Tom Petty song do you REALLY think Tom Petty is actually playing a Dsus4? No flippin' way. He's playing a Dsus. He probably thinks it's a Dsus4 but he'd be wrong.
So...when you see Dsus4 in a chart or a piece of music, whoever made that chart doesn't mean Dsus4, they mean Dsus - unless they're transcribing an Allan Holdsworth tune. In that case they might really mean Dsus4.
If you don't know who Allan Holdsworth is, that's too bad, because he died a week and a half ago. He was in a class by himself and if you are interested in seeing a true genius and an original voice on the instrument you should look him up. Start here.
Want to know more about triads? Including suspended triads? Go here.
How about Open Voiced triads like the Dsus4 above? Go here.
The next blog may be a rant on sus2 chords. I'm sure you'll be looking forward to that!