ctrlxmms is a small Perl script designed to increase the useability of XMMS. With it, you can use most of the common GUI functions of XMMS from the CLI. You also have a few handy commands which are not available from the GUI. Together with lirc and a remote (eg. Anir Multimedia Magic), this is a wonderful tool.
dagrab is a command line driven tool for extracting digital audio from cd. It works great with IDE drives (and others type too if the kernel supports digital audio read for them, I think this does not include SCSI drives for now), and supports jitter correction, filters and audio post-processing,as well as CDDB to automatically name your files appropriately.
DAP is a comprehensive audio sample editing and processing suite. It currently supports AIFF and AIFF-C audio files, 8 or 16 bit resolution, and 1, 2 or 4 channels of audio data. The package offers comprehensive editing, playback, and recording facilities including full time stretch resampling, manual data editing, and a reasonably complete DSP processing suite.
DarkIce is a live audio streamer. It records audio from an audio interface (e.g. a sound card), encodes it, and sends it to a streaming server. DarkIce can record from OSS audio devices, ALSA audio devices, Solaris audio interfaces, and Jack sources. DarkIce can encode into MP3, MP2, Ogg Vorbis, and AAC formats, and can send the encoded stream to ShoutCast, IceCast 1.3.x and 2.x, and the Darwin Streaming Server.
dave's cd player (dcd) is a simple command-line CD player. It plays CDs, loops (sequences of) tracks, plays tracks at random, and so on. Its a full featured, but simple-to-use CD player. It supports libmusicbrainz (musicbrainz.org) for CD information if desired, yet remains one of the leanest CD players out there.
DeuTex is a wad composer for Doom, Heretic, Hexen and Strife. It can be used to extract the lumps of a wad and save them as individual files. Conversely, it can also build a wad from separate files. When extracting a lump to a file, it does not just copy the raw data, it converts it to an appropriate format (such as PPM for graphics, .au for samples, etc.). When it reads files for inclusion in pwads, it does the necessary reciprocal conversions. In addition, DeuTex has functions such as merging wads, etc.
DigitalDJ is an SQL-based MP3-player frontend designed for people who want to create an MP3 version of their CD collection. It is designed to work with the Grip ripping/encoding application (but can be used separately). When Grip encodes MP3 files, it will place all of the song information into an SQL database. DigitalDJ can then use this information to create playlists based on a number of criteria.
Disc-cover provides an easy way to produce covers for audio CDs. It scans audio CDs and uses information from the CDDB or CDINDEX database to build a back and front cover for the CD. Output is in Latex, Dvi, PDF, Postscript, HTML, plain ASCII, or any other format suited for cdlabelgen.