-Classic Rock: I like the Beach Boys. If you just want to listen to fun in the sun type songs then "Summer Days (And Summer Nights too!)" is good. If you're into more moody stuff then you MUST get Pet Sounds. Still my favorite album of all time.
-Electronica: Recently got into Kraftwerk. Trans-European Express is one of their most famous. A lot of the early hip hop artists sampled it:
https://www.youtube.com/watch?v=ma8IgxHcAoE-Classical: I like a ton. Some of my absolute favorites are:
*Beethoven-9th Symphony, 2nd movement (much better than the 4th which has Ode to Joy imo. Lot of great tempo shifts.)
*Massenet-Meditation from "Thais." One of the most calming pieces ever written.
*Satie-Trois Gymnopédies: Gymnopédie No. 1. Another calming piece.
*Ravel-Bolero. A great study in repetition