Guayadeque is a music player that aims to be easy to use and fast even for huge music collections. It allows you to automatically or manually download covers, easily organize the music library, edit the ratings of the tracks, add labels to the artists, albums, and tracks, listen to shoutcast radios, download lyrics, show artist information based on last.fm content, and more. It includes a simple, built-in tag editor with picture support.
Khövsgöl is a minimal, highly configurable music player and browser. It can easily handle very large collections of music. It's designed for the GNOME desktop, but can run well in other environments. It works fine as a standalone player, but can also be used to remotely control music daemons such as MPD.
Packrat is a media collection manager application for Android. You can use it to add books, CDs, games, movies, etc. to your collection by scanning their barcodes and organizing them onto shelves. You can let Packrat organize your items into smart shelves, or manually stack items onto shelves of your own creation. You can also track items you don't have yet on a "wishlist" shelf.
jack-tuner is a musical instrument tuner that uses the JACK audio connection kit. It is a command line program, and it accepts many commands. The important ones are the tone and volume commands, which can produce any audible tone from 20hz to 20khz at a volume from 0 (silence) to 1 (loudest). It can also produce notes (for example, "tone D#" produces the note D#) over several octaves (for example, "tone C octave -1" produces the note C an octave below middle-C). It can also transpose notes (for example, "tone C > 5" produces G). There are commands to do microtonal tuning too. With multiple jack-tuner instances, you can tune chords. jack-tuner does not measure the note that an instrument is playing; instead you play the desired note with jack-tuner and tune your instrument by ear.