VLC Media Player - VLC is a free and open source cross-platform multimedia player and framework.
Mixed in Key - Mixed In Key is award-winning DJ software that gives you the #1 technique of the world's best...
AIMP - AIMP : Free Audio Player : Официальный сайт программы
Tunebat - A browser based song key and bpm database. Supplies compatible songs for harmonic mixing.
foobar2000 - An advanced freeware audio player for the Windows platform.
KeyFinder - Key estimation software for DJs