Tonality

Let’s start at the very beginning.

This song is in the natural minor.

Harmonic minor sounds vaguely Middle Eastern: composers use it to create an “exotic” or mysterious atmosphere.

Quarter-tone notation:

Some pieces for microtonally-tuned piano:

Turkish guitar music that uses microtones:

The music of the Second Viennese School in the early twentieth century used 12-tone scales.

Later in the 20th century, music attempted to break free of all tonal structures.

Remember: what you hear, and whether it sounds consonant or dissonant, is conditioned by your culture and by your own experiences as a listener.