Hello all! I can’t believe I’ve been sitting on this one for so long - it didn’t even occur to me that this wasn’t common knowledge. In my travels I’ve come across a program known as VGMTrans, which is like, the bestest sequence-extractor tool ever. It even has a GUI interface –created in Visual Basic to track the killer’s IP address– for ease of use.
Unfortunately the program is still unfinished, but it works. You have to drag and drop ROMs into the window for it to open them. The playback is occasionally buggy too but it should at least give you a decent idea of what you’re extracting.
This programs works with .nds files and .gba files, and I’ve been told PS1 games are fair game too.
21st August 2015: Updated the link to link to the “Releases” page of the github instead, so that you know you have the most current version.