I'm kinda late here and I see this thread is dormant for some time now, although it really really shouldn't because it'd be super interesting to see what people listen to while playing adult games.
anyway, I like to chill when I play story-driven adult games so I mainly listen to chill music: chillhop, jazzhop, lofi, this kind of jam(no vocals mind you). There are some beautiful mixes on youtube(and I'm sure on other sites as well) depending on the mood like city sounds mixes, rainy day mixes, afternoon coffee mixes, nightime mixes, summertime mixes etc. with hours of amazing music in each. I'd recomment you try it out, it helps with immersion and relaxation...it helps you feel the game more.
Also a honorary mention, in games in which a younger man tries to seduce an older woman(like Dual Family, A Wife and Mother, No More Secrets, Dreams Of Desire etc.) I used to listen to Lana Del Rey songs, especially "Young and Beautiful".