That was such a wonderful time for me, as an American teenager (the summer between eighth and ninth grade). Listening to these conversations brings so much of it back.
One thing I noticed: the hum. In all the audio recordings of Apollo-Houston conversations, there's a deep, ever-present hum that's not quite at the limit of audibility.
What struck me is that you would never hear that hum today; the reason is because all communications channels - including voice - would be digital in our time. Back then, they were analog. When you remember that it was often the case that Earth-crew communications were carried out via a huge dish antenna located somewhere other than in the continental US (I believe one such station was located in Woomera Australia) it is all the more amazing. Analog transmissions, over thousands of terrestrial miles. With so little hum.
This was more than a decade before NASA's TDRSS (digital) satellite system was put in orbit.
FYI: The Russian space comms did not have a hum either ...