I think ChatGPT got a bit confused, this is as close as I could get to what you are looking for:
from picard.metadata import register_track_metadata_processor
from syncedlyrics import search
def add_lyrics(tagger, metadata, track, release):
lyrics = search(f"{metadata['title']} {metadata['artist']}")
if lyrics:
metadata['lyrics'] = lyrics
register_track_metadata_processor(add_lyrics)
I took a peek at syncedlyrics and the search function returns a string in LRC format.
The problem is that I don’t think Picard maps the synced-lyrics tag. So when you do metadata['syncedlyrics'], you just create a custom tag (unless I’m wrong).
There is, however, a lyrics tag in the mapping. With the code above you would get the lyrics with some timestamps in the middle, so it’s definitely not what you are looking for.
BTW, I assumed you have already installed syncedlyrics with pip since you included it in the code.
I’ll look at it again later when I have more time.
P.S. I found this post from a few years ago where the same thing was asked. It’s linked to this issue.