Giada is a free, minimal, hardcore audio tool developed for DJs, live performers, and electronic musicians. It is available for Windows, Linux, and Mac.
MediaMonkey is a free music organizer for the serious collector; it will manage a music library consisting of small to extensive collections (50,000+) of audio files and playlists.
DeskFX audio enhancer software is designed to modify and enhance the music and audio played through your speakers and headphones to provide you with the best possible sound experience.
iDevice Manager offers access to the device file system, creates its own ringtones from MP3, displays SMS messages, plays music and many more useful functions.
Boom 2 is an audio enhancement app that helps improve your Mac's audio experience by providing rich and immersive sound through a robust interface geared for audio.
Mixxx Portable, offered by PortableApps.com, is a robust audio player with everything you need to start making DJ mixes in one package. Installer and 32-bit are also available.
OpenMPT (Open ModPlug Tracker) is a freeware tracker software for Windows that allows you to create and playback music on your machine. Portable version is also available.
OpenMPT Portable, also known as Open ModPlug Tracker, is a free tracker software designed for Windows; you can easily create and play music on your computer. Installer version is also available.
VB-Audio Voicemeeter is an all-in-one audio mixer application that includes a Virtual Audio Device used as virtual I/O for mixing and managing any audio source from or to any audio device or application.