lesson vs music lesson

lesson and music lesson both are nouns.

Word	Noun	Adjective	Verb	Adverb
lesson	Yes	No	No	No
music lesson	Yes	No	No	No

As nouns, music lesson is a hyponym of lesson; that is, music lesson is a word with a more specific, narrower meaning than lesson:

Other hyponyms of lesson include language lesson, dance lesson, tennis lesson, golf lesson.

lesson (noun)	music lesson (noun)
a task assigned for individual study	a lesson in performing music
a unit of instruction
punishment intended as a warning to others
the significance of a story or event