Major Add 9’s are great chords without being overly complex. The triad on strings 2/3/4 plus the 9 on the top string is a personal favorite, as is the movable form of the open C (add9). The root-3 version is really more of an inverted Mu (1/2/3/5) chord which I’ll dig into later.
There’s a lot here, and for good reason. On their own, fourths are pretty useful. They work great as double stops, they’re inverted fifths from the top note, the ♯4/ ♯11 is the heart of Lydian & shares the same address as the blue note, and they’re almost always easy to play. Something I’ve only recently learned (from Truefire’s Interval Insights) is how many great approaches and departures there are from fourths. Hammers up to the major 2nd, up from the major third, and even up to the fifth or from the minor third all sound great from the perfect fourth. I’ve yet to experiment much with the ♯4 and it’s neighbors, but my sense is the 5th provides a nice resolution.
Hammering the root up to the second creates a nice minor third of its own and also provides the top two thirds of a C-shape triad on the lower string if you bring your pinky into the mix. You can’t help but hear Hendrix with this lick.
I’ve had trouble finding good simple charts of spread triads. Rick Beato did a great video on them recently, but I had trouble finding a simple reference for spread triads in his book (which I’d highly recommend here, as it is freakishly comprehensive). I figured it was worth working out my own reference to share on Pedal On. Here are the major spread triads with their bass note on the lowest string. They aren’t all easy to play, but they sound great. I’ll work across the strings and then into minor and maybe beyond.
I didn’t realize just how useful learning all of these triad positions would be until they started clicking, particularly up and down between the three core shapes in a given key (root on string 2, 3, or 4). Beginning with the shape below as the I chord gives you a ton of options nearby. The ii, IV, and vi have multiple options that are easy to grab or switch between.
With a bassline or second harmony covering the low end, you can easily cycle through the upper extensions of the underlying chord (upper structure triads once you’re beyond R,3,5 if I recall correctly). Throw sus2 and sus4 in and your palette extends even further. I should probably record an audio example to demonstrate.
The best thing to me is that you can always map a diatonic mode back to a home Ionean key, so just knowing which I chord you refer back to means you can grab extensions up and down the neck. For instance, A Aeolian is just the sixth mode of C Major, so all of the triads will be the same as those in C. Even grabbing the C Maj triad just gives you an Am7 over an A bass note.