As it was so heavily inspired by games of the 1980's, it seemed necessary that it have a soundtrack to go along with it that fit the '80s retro aesthetic. And so, game creator Edward McMillen hired composer Danny Baranowsky to write and perform the music for the title.
The above track, "Betus Blues" plays during the second world of the game, "The Hospital." It's in my opinion, the best song on the soundtrack, but also stands out as a wonderful piece of gaming music in general.
The use of keyboards evokes the old, 8-bit gaming sound considering that all the music back then had to be synthesized with sound chips that were only capable of doing so much. All the instrumentation back then had to be small variations of "bleeps" and "bloops." Today you an actually have real instrumentation inserted into a game, but Baranowsky opts for a sound that is intentionally dated, and it works.
The percussion track is strong but the layers of keyboards are what really sells the song. The overall tone is somewhat dark and ominous, especially to start, but the tone lightens up around the 15 second mark. The real hook comes in at 29 seconds when Baranowsky lays out a melody that is immediately arresting and engaging. The rest of the song goes back into the much darker sound with the more electronic keys still popping up to provide something more than just atmosphere.
Like game music should be, it's relatively short, is fun to hear repeated, doesn't get old, and fits the spirit of the game exceptionally well.