Everything Michael said. But, the lines from Britney are - "My loneliness is killing me. I must confess, I still believe. When I'm not with you, I lose my mind. Give me a sign. Hit me, baby, one more time." Which are grammatically correct. So, no double negative. That said, songs often have double negatives and otherwise mangled grammar. (examples - "Ain't Nobody's Business if I Do" or "Is You Is or Is You Ain't my Baby?" or "(I Can't Get No) Satisfaction") Feel free to sing along, but don't try to speak like this without musical accompaniment.

Pop songs are full of abbreviations, slang, bad grammar, and apparently meaningless lyrics. Having said that, Adele's words are correct. "a thousand = one thousand = 1,000" "a" relates to "thousand", not times. "Let the sky fall" is a causative verb expression. "let" is the causative verb in the imperative, "sky" is the object, and "fall" is the main verb. Sia - abbreviated form - not correct. Britney - "Hit me, baby, one more time" is the full sentence. Double negatives are slang and universally known to be incorrect. There are numerous other songs e.g. "Ain't no sunshine when she's gone." "Ain't no mountain high enough" "There ain't no pleasing you"

Aleksey, there is another example: But it don't matter, it clearly doesn't tear you apart anymore (Adele, 'Hello')