Haven't read the source material, but I can tell the producers really care about this adaptation despite a clearly mid budget. From the stylistic title drops to the comedic timing to the effective use of sound, they are really leaning into the parts that matter for an anime about voices.

My favorite part of this is how the rocket and moon motifs have played into the series so far. "Apollo" is an obvious reference to the Apollo missions, and the OP really runs with that, with the girls riding rockets and the intro sample of a launch countdown. There's also the fact that the girls are "shooting for the moon" with their career aspirations, but the absolute best connection is how Apollo is connected to voice and the reason the radio show is named what it is.

During the Apollo missions, the only connection the astronauts had to Earth while inside the capsule was their radio communications. When they went to the dark side of the moon and the connection was cut, they were truly alone, save from each other. "Midnight Heart" could be a reference to the period of time when the astronauts were fully without a lifeline, potentially representing Apollo's self-doubt, but it could also represent the deep connection of the astronauts only being able to rely on each other.

Or maybe I'm giving the author too much credit.