https://de.wikipedia.org/wiki/Guayadeque_(Audioplayer)

auf Last.fm basierte intelligente Ergänzung der Wiedergabeliste (sog. Smart-Mode, d. h. es werden weitere Lieder automatisch hinzugefügt)

Intelligent addition to the playlist based on Last.fm (so-called smart mode, i.e. additional songs are added automatically)

The feature would automatically add songs based on their similarity to the currently playing track. The proposed feature involves scanning the local library and utilizing last.fm "Similar Tracks" feature to identify and add songs that are similar to the current one.

Example
https://www.last.fm/music/Letzte+Instanz/_/Rapunzel

• Track: Letzte Instanz - Rapunzel
• Simlar Tracks: Schandmaul - Walpurigsnacht; Ignis Fatuu - Spiel des Lebens; Cultus Ferox - Goldene Zeiten

Implementation
According to https://github.com/anonbeat/Guayadeque, the player is written in C++, which might make it possible to utilize some of its existing code.

My limited understanding is that https://www.last.fm/api/show/track.getSimilar could be used for that feature.

Alterantives
I found another tool called https://github.com/teticio/Deej-AI that seems to scan the music and create a playlist from that rather than dynamically updating the playlist with similar tracks in real-time.

I think it might be unique addition to the player