I know very little about this device and only recently even heard that it existed; however, what I have learned is that at some point Teenage Engineering and Kayne West collaborated to release a small audio player for the Jesus Is King album but the audio gadget was never released. Apparently thousands of these devices were produced and then, when the release was cancelled, sold to third-party resellers like New Republic from whom I purchased my own copy.
The player doesn’t just offer an expensive and over-engineered method of playing Kanye’s album: each of the four buttons and faders on the device corresponds to certain elements of each song (commonly called “stems”), allowing the listener to customize the sound of each track. Each stem can be played independently or in concert with other stems, greatly changing the way a track sounds. Additionally, some common Teenage Engineering audio effects were included within the device to further alter each track.
What makes this even more interesting to me is the community of fans who spent hours looking through the device to learn how it works who eventually discovered how to add new music to the memory. Now instead of it just being a Kanye West concept, this device has become a small four-track audio player that can be connected and even synchronized with other Teenage Engineering devices. The online tool I used allowed me to take a four-track WAV file I made in Audacity from compiled public domain and Creative Commons audio files I found on FreeSound.org to use as background audio on music I produce on the EP-133 I just bought.