Back 2 U (AM 01:27) by NCT127 talks about a breakup between two people and how one of them wants to fix things but the other one is hesitant about it, so it doesn't pick up their calls, and when they do it, the other person is being manipulative, cuz they still love them +

and it hurts to hear them cry, but in the end they're firm about how they feel about their relationship and end things with them asking them to not contacte them ever again, because they're not, in fact, running back to them.
this person represented as their now ex partner is +

only interested in materialistic things, see the lyrics "But you’re too much for me, the cash, the diamonds and pearls you spend, you’re buried in flashiness" still this person is using their cry to gain them back and manipulate them so they feel guilty and go back, +

then at the end we can hear jaehyun saying:
"I barely fell asleep late at night
The ringing sound wakes me up
But I turn around and close my eyes"
meaning they are finally taking control over the situation, not letting the other person manipulate them and ignoring them for good+

now let's TALK ABOUT SOUND AND MUSIC (which i don't know shit about bUT I WAS READING AND WATCHING VIDEOS ABOUT IT!!! I have an approximate amount of knowledge) so you can hear in the beginning the phone ringing as it fades with the piano notes, and wow then the echoes??? this +

is important because it represents how repetitive the situation is, and then Mark says "i'm not going back" and the percusion starts, to give rhythm and the first verse begins, then in Taeil's first verse as he sings you can heAR SOME BAD ASS HARMONIES BRO! (the "please")+

and Doyoung finishes his verse and there's a sound idk how to call it but we will call it a suction sound cuz it feels like the original instrumental disappears and other one begins when they start singing the chorus, whICH IS FUCKING GORGEOURS CUZ THEY SING SO GOOD I LOVE VOICE+

then you have Tae and Mark's verse AND IT CHANGES THE FLOW AGAIN KINGS !!!!11!!1!! and we go back to Dotaeil doing their beautiful harmony thing.
after that 2nd chorus you have the??? bridge?? idk it's doyoung and haechan's part and i LOVE HAECHAN 'S VOICE OK!! +

and TAEIL DOES A GOOD AMAZING JOB HITTING THAT NOTE!! but WAIT THER'E S MOREEE!!=!!=="=" AND THAT IS that the MUSIC FADES ONE MORE TIME snd you're left with vocals anD PERCUSIONS !!! THAT MEANSD!!! we're getting the striking part!! they're a bout to fucK IT UP KYLE!!! +

they're singing the chorus and then KING MOON TAEIL HITS A GOD KNOWS WHAT G5+ NOTE WAS THAT BUT WOW I SHIVER EVERY FUCKING TIME !!!111 !!! and then the suction sound goes back wow i am hyperventialtinf and then the chorus BUT IT DOESN0T STOP THERE, THERE'S MORE THESE ABSOLUT+

BEASTS DO A NFUCKING SCALE??? they sinng "don't look for me again" IN A FUCKING SCALE THEY GO !!!????????
amazing my ears were blessed to hear that
and thenn the 3rd chorus comes back with instrumentals and the freaking adlibs man....wow.
and to end the song +

jaehyun, the absolute madman, he,.,,,, he goes'??
"I barely fell asleep late at night
The ringing sound wakes me up
But I turn around and close my eyes"
with his deep ass voice i fgpljfdv nldskgv bg

BVERY WELLL but its not over well almost then you can hear the missing call so+

sound, LIKE THEY DIDN'T PICK UP THE PHONE CUZ FUCK THAT BITCH THAT MADE ME SUFFER!!!!!

and with that i end this thread of deep, meaningful and scientific analysis about NCT127's best track, Back 2 U (AM 01:27).
thanks for reading or whatever