So after Googling around I found a few different people in very old threads who had this same issue as me, but no fixes. I'm crossing my fingers and hoping that a solution has been found since those times, however.

Basically on the New Vegas radio station, I'm hearing the same few handful of songs (10 or so?) over, and over, and while enjoyable, I'm getting kind of burnt out on them. I swear I remember there being more songs in Fallout 3, so I was Googling around to find a way to increase the songs. I found a thread saying that if I had songs from an external source, I could dump them in New Vegas's data folder to get the radio to play them. So I navigated to the data folder where these songs are, and I found a handsome collection of songs--48 MP3s to be exact--of which only a handful are playing.

So as most of those aren't playing, I doubt dumping in another 40 songs would help either. Besides, I trust gamesas's judgement more than grabbing some hit tunes of the 50s and assuming they fit in the setting.

I Googled around, and as I before mentioned I found a few really old threads on this issue, with no announcement of "fixed!" or a solution that made sense. I tried one of the solutions anyways--a codex download--which did naught.

Any help, advice, or anyone who's been through this same thing?

It's not enough to just put the songs in the songs folder - you have to modify the radio station playlist to get the game to recognize and play them.

You'll need a mod for that - there's several of them listed on this http://newvegas.nexusmods.com/mods/searchresults/?src_cat=88 that will allow you to generate custom playlists for Radio New Vegas and Mojave Music Radio. Make sure you carefully read the instructions for these mods - the game can be very finicky with music files when it comes to things like formats, bitrates, sampling frequencies, etc. of the files you use.

The Nexus is almost unuseable today, probably due to high traffic. You'll have to be patient when you go there.