*One album per artist/band.
*Major blind-spot from 70's to mid-80's. Seriously, not my favourite era.
*No metal, hip-hop or punk because I'm not well-versed in any of those genres.
*Chose exclusively critically acclaimed albums to reduce the amount of ensuing butthurt.
"Typical" Alpha Genres: Progressive rock, psychedelic pop, math rock, shoegaze, progressive metal, japanoise, harsh noise, IDM, certain brand of pop music similar to of Montreal whatever it's called, early 90's indie rock, Pavement, Sabadoh et al.
"Typical" Beta Genres: 70's punk rock, glam rock, grunge, psychedelic rock, 90's hip hop, um drawing a blank.
"Typical" Gamma Genres: post-hardcore, idk, gamma is still the most elusive quadra to me.
"Typical" Delta Music: bubble-gum pop, 90's indie pop, twee, singer-songwriter, folk pop, folk jazz, certain brands of punk, (and I guess if Absurd's taste is to be considered) Oi! et al.
 Excludes "contemporary" music or very wide umbrella terms like "indie" or "pop". Also doesn't include styles (i.e. "electronic") but the themes, mood, etc. Stereotyped and exaggerated on purpose.