dategrep searches the named input files for lines matching a date range and prints them to stdout.
If dategrep works on a seekable file, it can do a binary search to find the first and last line to print pretty efficiently. dategrep can also read from stdin if one the filename arguments is just a hyphen, but in this case it has to parse every single line which will be slower.
SoX is a cross-platform (Windows, Linux, MacOS X, etc.) command line utility that can convert various formats of computer audio files in to other formats. It can also apply various effects to these sound files, and, as an added bonus, SoX can play and record audio files on most platforms.