Utwór, nutka, and kawałek. What's the difference?
Very often while reading Polish and seeing people speak online, they all refer to these words as a "song."
My question is what is the difference between all these and which is most common or acceptable to use and when?
"Utwór" is a normal word for a "piece", for example in music or poetry so it's helpful especially when you can't call music "piosenka" (a song) as no one is singing there, it's instrumental. But you can use it for a song as well.
"Nutka" is a diminutive from "nuta", a musical note. So that's definitely totally colloquial. I rather hear "nuta" about a song, don't know if I heard "nutka".
"Kawałek" is more literally "a piece" - also a piece of cake even, and it's colloquial as well, although not that much as "nutka".
So the acceptability of these words, from the highest, would be: utwór - kawałek - nuta - nutka.