Brawl Song Manager is a program that uses BrawlLib to quickly view which BRSTM music files are installed on your SD card (or in whatever folder, on whatever device, you use for Brawl hacks.)
The left side of the window has a list of .BRSTM music files in the current directory; you can change the directory through the File menu. When you choose a .BRSTM file, the right side of the window will display the playback module from BrawlBox, allowing you to listen to the song. A text box on top will show the song title from info.pac; to edit the title, change the text in the box (for one or more songs) and press Enter.
See the readme file (BrawlSongManager.txt) for more information and recent changes.