Aziraphale isn't as opposed to modern music as he seems. When he starts spending more time at Crowley's flat, he starts to see that the demon's taste runs eclectic and, interspersed with flashy bebop, are some sad, slow songs that speak to the soft, worldly being inside that Crowley never lets anyone see. Or never lets anyone else see, he thinks with a significant amount of smug satisfaction.

Aziraphale falls in love, bit by bit, with the crumbs of Crowley's soul he finds in those songs. One night they're drinking and reading, respectively, sharing space and companionship without purpose outside of itself (something somewhat new for them - not needing to fill the leaden air with words in order to drown out the tension running rampant beneath) and he hears Crowley softly sing along to the end of a song and it strikes him right in the chest:

Follow me through / a city of frost covered angels / I swear I have nothing to prove / I just want to dance in your tangles / to give me some reason to move / but to take on the world at all angles / requires a strength I can't use / so I'll meet you up high in your anger of all that is hoping and waiting for you

And he can feel them in those words. Can see the map Crowley has made of his feelings throughout the decades, kept to himself until now.

My bois Gardenhead, Bootleg!Gardenhead, Murder!head and Dragon!head

Yeah Gardenhead is A Nonbinary dude/Demiboy/Genderfluid now