This is a discussion of basic music harmony. It includes scale structure, intervals, chord structure and chord progressions. I am hoping to provide a foundation for discussion of some more complex musical topics in the future.
I love the Beatles classic, Yesterday. It is a very sophisticated song, sweetened by a string section and arranged by the talented George Martin. There is syncopation, as in most Beatles songs, a suspended chord for interest, and Martin uses counterpoint to bring out the melody of the song and to provide a nostalgic feeling to go along with the lyrics. I have loved this song for a long time, and years ago I worked out an arrangement to it. Play it as it is, or use just the elements you like. Either way, have fun.