Building Major and Minor Triads
The key point in this video is that if you understand the interval relationships between each note of a triad, you'll be able to easily form a triad in any key, anywhere on the piano.
For major triads, the interval numbers to remember are three and two. This means that between the bottom and middle notes of the triad, you will have three keys that are not pressed down. In between the middle and top notes of the triad, you will have two keys that are not pressed down. So for a C major triad, your notes will be C, E and G. In between C and E, you have three notes not pressed down. In between E and G, you have two notes not pressed down.
For minor triads, it is just the opposite--you should remember two and three. Another easy way to form the minor triad is to first form the major triad and then move the middle note down one half step. So for a C minor traid, the notes would be C, Eb, and G. In between C and Eb, you will have two notes not pressed down and in beterrn Eb and G you will have 3 notes not pressed down.
If you understand this concept, practice building triads anywhere on the keyboard. Just pick a root note and then build the triad. It's as easy as that!