What are the differences between a dominant 7th chord and a major 7th chord, and how does the use of each chord type impact the overall harmonic structure of a piece of music?

The main difference between a dominant 7th chord and a major 7th chord is the interval between the root and the 7th note. In a dominant 7th chord, this interval is a minor 7th, while in a major 7th chord, it is a major 7th.

The use of each chord type impacts the overall harmonic structure of a piece of music in different ways. Dominant 7th chords create tension and are often used to lead to a resolution, adding a sense of movement and instability. Major 7th chords, on the other hand, create a more lush and dreamy sound, adding a sense of sophistication and stability to the harmonic structure.