You could start with a simple experiment using DeepSpeech[1] as an automatic transcription tool (I assume these recordings are non-public, so you'd prefer a local service instead of a cloud solution, which detection rate would probably be better).
After having the text auto-transcribed into a simple txt file, I would check the quality and do some manual corrections, where required.
Then import the transcribed text into the audio file metadata (e.g. Lyrics, Description or Comment, depending on your metadata format).
The relevant fields I would look at are:
Description
LongDescription
Comment
Lyrics
Group
Title
Album
Composer
Depending on the length of the recording you could also add chapters. Here is a nice audio book guide with some further ideas:
https://github.com/seanap/Plex-Audiobook-Guide?tab=readme-ov...Now you should have access to the metadata via audio player - maybe even a search would be supported.
[1]: https://deepgram.com/learn/guide-deepspeech-speech-to-text