-Switched On Pop - pop songs from a music theory + culture perspective, hosted by a musicologist and songwriter. A lot of "ephemeral crap," as Ben Marlin put it to me, but it's neat seeing how much real craft and thought goes into even the stupidest music, and they make some convincing comparisons to concepts from classical music.
-Between the Liner Notes - Long-form explorations of music history. I'm only four episodes in, but there have been examinations of early MTV, the "tuning wars" (which are surprisingly heated!), and advanced Nazi reel-to-reel recording technology.
-You Must Remember This - Deep dives into stories from "Hollywood's first century." Some of the episodes are just straight celebrity bios, but there are deeper explorations of wider and unknown industry trends as well, and the host really knows her shit.
-The Flop House - The only "nerds shooting the shit" podcast I can stomach, because my wife loves it and I've gotten used to the hosts. Deep dives into recent bad movies destined for obscurity, with a lot of funny tangents.
Also four lectures into the Greenberg How to Listen to Great Music series, and his very pointed delivery and sense of humor makes for an easy way to digest some pretty heady (and interesting!) concepts.