NDS Sound Extractor is a command line program to extract sound sequences and samples as .midi and .wav from a DS ROM. The original site for it does not have the program anymore, so you may get it from here: [1].
Usage 
Edit
Usage : ndssndext.exe [options] Options: -x extract files only (no decoding) -s show processing status --help show this usage
You can also drag an .nds ROM onto the program and it will automatically create a folder and extract mid and wav files inside subfolders named Sequence, Stream and WaveSample.
Extracting Raw Data Edit
This program can also extract the raw .sseq, .strm and .swar files without converting them with the "-x" option:
ndssndext.exe -x file.nds
