Titles on classical releases should mostly follow the printed information, with addition of the overall work title to movement tracks (see below), and any changes required by the language-specific classical guidelines. Note that many classical releases have a less detailed tracklist at the back and a more detailed one in the booklet. When choosing titles, it's generally better to follow the more detailed one, if available. Don't add extra information to the title (key, catalog number, etc.) that is not on the printed tracklist (see below for more).
Overall work title
When the release's printed tracklist groups tracks that are part of a work together under a heading for the overall work title (with the printed track titles being movement or part titles), then add the overall work title (as listed in the heading) to all tracks from the work, separated with a colon.
As on cover:
And not only for the first track:
Do this even if the overall work title is only on the release title (for example, in a release that contains only a full performance of the Goldberg Variations, the first track title should still be something like "Goldberg Variations: Aria", not just "Aria").
Similarly, for operas, oratorios, cantatas and other works divided in acts/parts, do mention the act or part on all tracks, not only the first track of each one.
If a track which is an extract of a larger work is listed on the release as "Part from Work" (e.g. "Allegro from Symphony no. 5") or as "Part title" (e.g. "Una furtiva lagrima") just enter it as-is, there's no need to turn it into "Work: Part".
Extra work information
Do list key, catalog number, movement numbers, etc. if they are included as part of the titles on the release, but not otherwise; that information is already available at the work level, so it doesn't need to be forced into the track titles if the release doesn't include it. "Sonata no. 1: Allegro" is a perfectly acceptable track title, if that's what is on the release. Similarly, do not "complete" the information: if a release says "in G", there is no need to extend it to "in G major".
Keep in mind the language-specific guidelines override these. If a language guideline specifies a change should be made, then follow them (for example, the English guidelines require "in" to precede the key name). Otherwise, enter the key, catalog number and movement numbers as printed on the release.
When a release has titles in several languages (for example, English / German / French), enter the tracklist in the main language of the release. If all languages are given equal weight, just pick one. The others can be entered as pseudo-releases and linked to the release marked as official with the appropriate relationship.