Jenseits von Eden ("Guardian Angel" as it is known in its English name) is a song made by Masquerade, a musical project that originated in Hamburg, Germany in 1983. The project was created by German artists Drafi Deutscher and Chris Evans-Ironside. The song was heard faintly in the background of Tape 6, during Jonah and Gabby's reunion. The reason why this song, as well as the rest of the Season 1 OST, was added, is because the Mangan Sisters used music from free online music sources, like the Internet Archive, as they confirmed. The song is a breakup song originally, as "guardian angel" is used in a romantic context. In 1967, Deutscher got into legal trouble/controversy that gave him negative media attention, thus prompting him to perform under various aliases. The song has been translated into various languages, such as Czech, Italian, German, and many more.
Both voices in "Guardian Angel" are performed by Deutscher himself. The iconic "striking" sounds heard in the intro are the "Orchestral Hit" preset (Orch 5) on the Australian synthesizer, the Fairlight CMI. Because of the previously mentioned legal trouble, Drafi, with the assistance of Intersong (now Warner-Chappell in Hamburg), hired two substitutes to dress in suits and makeup, and lip sync to Deutscher's music. The identities of these performers have since been debated, but it has been confirmed these men are Geunter Urban (black suit) and Ole Olsen (white suit).
While some have made tribute videos to the song on YouTube (in correlation to the series), there are many YouTube channels dedicated to Masquerade that will help provide more information on Deutscher, the performers, and Deutscher's discography.
The two main channels that are still active in terms of Masquerade content are Whit87 and Masquerade1984, two enthusiasts on the project.
There was another channel called Masquerade1983 (no relation to the other channels), who posted Masquerade content throughout the entire 2010 year, before eventually going defunct as on 03/29/2010, their last video being of a performance of Guardian Angel on Eldorado, a Danish TV music program.
The album Guardian Angel originates from can be listened to here.