I've been following the foundation and technique I course, and I learned the C major triad horizontally & vertically. I am currently having trouble learning the other keys for the major triads. What do I have to do to learn the different keys and master the major triads?
I think you need to spend some time visualizing the fretboard. If you can visualize the shapes of the triads (let's say on the first three strings ( EBG)), then do what Tomo is doing in the triad lesson i.e., play 1-4-5 (C-F-G) triads to a metronome. This way you learn the triads in F and G key as well. Once you have mastered this, then switch your key (to let's say A), that is play the 1-4-5 triads of the new key (A-D-E), and so on and so forth. This way you are learning triads in multiple keys, plus, also training your brain to follow chord changes.
One of the biggest mistakes I have committed in my guitar journey is not spending enough time learning one concept and moving on to newer concepts. I am now learning the easy, slow, enjoyable way: just do the C-F-G triads (1-4-5 blues progression) really slow, speed it up gradually, visualize the notes, know whether you are playing 1-3-5, 3-5-1, or 5-1-3, what notes are you playing (CEG, FAC, GBD). Just do this on the first three strings, before moving onto more strings. Sing the notes as well, so that you internalize the sound of the notes. The joy lies in learning something really deep, so just believe in the process and practice daily|
very helpful. thank you