Should they be separated by a colon, comma or put in parentheses? Should they contain quotation marks and if so, which ones? Double quotes ("incipit") or as written in the booklet (that could be «incipit», „incipit“, “incipit” etc depending on the language)? Or should they be omitted if the track can clearly be identified from the work title?
An incipit is the opening words or lines of a text, in this case lyrics. It’s sometimes used in place of titles especially for archaic works which may not have an actual title.
The case I’m interested in is when the song’s title AND the incipit is given. Take for example track 2 of https://musicbrainz.org/release/2d45a158-ae1e-4967-b2cf-7ad79c581934.
Here, the submitter of the disc chose to add the incipit in parentheses and replaced the guillemets («incipit») with hyphen-minuses (-incipit-).