This simple approach to harmony is not without its pitfalls.
If you follow interval-based approach religiously, you will find that every now and then, you will play a note tht just doesn’t sound right.
a. falling outside the chord
–when you play a consttant-interval harmonic line you are assuming that the melody always falls on the root of the underlying chord. Everything is great if the melody is C and te underlying chord is a CMchord.
–if youplay a 3rd (E) above this note, you are playing the 3rd of the chord which sounds fine.
–if melody note is E, the third of the chord, and youlpay a G which is a 5th of the chord, it’s fine.
–but what if the melody doesn’t fall on the root or the 3rd of the chod — what if it falls on the fifth instead? a 3rd above that will be B, which is the 7th of the chord.
–the 7th isn’t part of the basic triad, instead you are now playing a chord extension.
–now playing the 7th of the chod isn’t necessarily wrong; in fact, under certain circumstances it might sound really cool. More often than not, playhing an extended note like this doesn’t sound quite right. Your ear expects to hear a tone that falls within the chord triad, not a chord extension. In these instances, the harmony note sound dissonant.
–dissonancce is fine for short periods of time, but if it occurs on a note that’s held for a long period — a half note or a whole note, it starts to grate on the ear.
–the key to avoid this type of dissonance is to chnge the offending note to one that is contained within the underlying chord. Change the B to a C and for that part of the song, your h armony interval shifts from a 3rd to a 4th and the note now fall solidly within the underlying chord.