Youki is a free software media player for most modern Unix operating systems. It is a superficially simple player, but under the hood features a library based on MusicBrainz-IDs from the ground up, and specific features to make searching in tracks faster, such as an iterative set-combining and caching algorithm (ISCC) and Markov-tree based text prediction for faster access to the music. It features a DJ-ing plugin using local statistics such as a Markov tree for track transition prediction, linear playback statistics and Last.fm data to provide the user with a random yet tuned experience to the user's music when using the plugin.
The official website (youki.mp) seems to be gone for good. The author has created a so-called Personal Package Archive (PPA) on Launchpad for the Ubuntu Linux distribution that still holds the source code of the last version as well as binary packages. See https://launchpad.net/~internalerror/+archive/ppa .
Youki is the current media player of the MPX Project. Previous media players produced by the team were Beep Media Player, BMPx, and the never officially released audiosource. Youki shares virtually no code with the older Beep Media Player or BMPx and was instead written from scratch. The only component kept in its basic outline is the BMPx-originated GStreamer-based playback engine, which has since been rewritten and refactored.