What is "microtones"

Usage examples of "microtones".

It was also because of the radio that she discovered that there were beautiful songs for women, and she sang `O Mio Babbino Carol at the top of her voice as she scrubbed the floor on her hands and knees, investing it with oriental microtones and adorning it with ululations, thus abnegating in the very attempt her project of becoming Italian.

You know, chromatic scales and microtones, and all sorts of crashes and bangs and squeaks and noises from lawnmowers, but it's only the experts and critics who don't realise what dreadful rubbish it is.