On Music Making

For example, the song It Must Have Been Love - Roxette. Left hand thinks (single) bass notes, degrees or steps of a scale. Right hand adds harmony by thinking 1 or 3 or 5 or 7 or 9 or 11 or 13 above bass. Singer sings melody. That's all. The particular example song is written on C major scale. So the seven notes on our ususal music universe (do re mi fa sol la si) are all natural corresponding to the white keys on the music keyboard. Bass begins with C (tonic of the scale) so chord is C E G. Then bass chooses the subdominant of the scale which is F and chord becomes F A C. For best sound results we may use the least possible change of notes on the right hand (see principle of least change in music). So progression from bass F to Bass D is played F A C to F A D instead of D F A which sounds trivial or wrong. (from a discussion with Vicky). Further reading: Bach Bass Rules - Niedt, Bach