What if I don't want my music on the cloud? I just got my Nexus 7 tablet and I was trying to load some music/videos to it. I have about 10 gigs worth of .mp3 files with no DRM in my computer. Since this is Android, I figured I would not be subject to the pain that is iTunes and I would simply be able to drag the music into a "Music" folder if I plugged in the tablet to my computer. Sure enough, I saw a folder named "Music" and tried dragging a couple of files to it. When I go to my Nexus, however, I don't see the files. I started reading up on this and it seems that the way to do things on Android is to use the Google Music Manager which would then put my songs in "the cloud" and make them playable from any device. That's all nice and everything, but is there any way to simply put a couple songs into my device locally without any of that funny business?

TL;DR: I don't want to use Music Manager, how do I locally upload a song/video to my Nexus 7?
Android uses a so-called Media Scanner to index your media files (this also applies to your images and videos). This Media Scanner ships with the system, and fires automatically on certain system events -- such as after boot, or when you insert your SD-Card. It does, however, not react on a simple "file-drop" via network. For such cases, it might need a little help to get to know it has to act:


Rescan Media
Rescan SD Card!


Are two free example apps from the playstore which do exactly that: trigger the Media Scanner. Once the Media Scanner has indexed your new files, they will immediately show up in the corresponding apps such as the gallery (for images/videos) or your music player.