The 6th video for Week 1 of Fundamentals of Music Theory is a 4:15 second piece called “Primary chords and their application“. Dr. Worth begins the video by recapping that we’ve found 7 triads that we can derive from the major scale. I believe that what he’s referring to are triads with root notes started on each note of the scale. So, in C-major (C-D-E-F-G-A-B) we’d have a triad with a root of C, one with a root on D, the next on E, etc.
He says that we’re going to focus on the 3 major ones, which are C, F and G. I believe that those are major because we’re working in the key of C, and in that key, [C is the 1], [F is the 4] and [G is the 5] – which is also called a I-IV-V chord progression. In a major tonality, the 1, 4, and 5 are major.
Worth explains that these chords are important in common practice classical music, jazz, pop, rock and folk music. Their use is sometimes referred to as the “Three Chord Trick”. Yes, that does sound like a derogatory name for a musician. He then walks us through each of the three triads that we’re going to look at.
- The C-major chord, which starts on the tonic, or 1, and is called the Tonic triad
- The F-major chord, which starts on the 4th degree and is called the Sub-dominant triad
- The G-major chord, which starts on the 5th degree and is called the Dominant triad
Now, these are just names. The names tell us their function in the scale they’re derived from, but I personally just think of them as the I, IV and V. This also helps me figure out which finger and fret to use to find them, based on where the tonic, or 1 is. Of course, that’s because I still use this info with one of two major scale patterns that I know.
What he says next is important to bassists and applies to most Western music: When we’re harmonizing a melody its normal to have a melodic note be a member of a chord that’s backing it. We can expect to hear a strong melody note existing in its chord.