Contents pagesList of characters - for each character please:
- state the type of voice needed for that character (e.g. lyric mezzo)
- ideally give the bottom and top notes for that role (and maybe even the tessitura)
- list every scene which that character is in, with scene titles and page numbers, maybe indicating if it's just spoken, or if the character is present without speaking or singing
- also include a "chorus" section that lists every scene where there is chorus (sung, spoken, chorus just present in the scene), with scene titles and page numbers.
- list every single scene, the more the merrier (if I see another contents page giving page numbers for just Act 1 and Act 2 and nothing else, I shall scream)
- state exactly which characters are in it (yes including recits or spoken lines only, yes including chorus).
Main bodyAt the top of the first page of each scene, again list exactly which characters are in it (yes including ones doing recitatives or spoken lines only or just appearing in the scene, yes including chorus).
Don't forget to add rehearsal numbers. Lots and lots of them.
Don't please please please don't split libretto and music into different sections so users have to flip back and forth between them when one scene has only dialogue and another music. Run them together in the right order, alternating pages of dialogue and music if you have to - and please include all dialogue or recit that's interwoven with the music at the right points in the music. (Ahem particularly aimed at MTI. Grumble grumble.)
Word by word translations of scores not originally written in English would be the icing on the cake...
Similarly for collections of songs or arias - why not include the name of the character who sings it (and gender if not obvious), and the title of the scene it's from, as well as the name of the original opera/musical for each song? How much extra ink does that cost, for goodness' sake? Some Sondheim collections are particularly bad in this regard.
Never mind scholarly editions, many of us just want scores which are genuinely practical and usable. Sure, what I've suggested would involve some extra work and cost, but not that much extra (if you ignore word by word translations), and they'd only add a few more pages to the score, yet make it immeasurably more helpful to singers and actors.
Especially for out of copyright works, there may be quite a few competing scores available. Some music publisher could really differentiate itself by adding value in the simple ways I've requested, and corner the market in vocal scores. It's a niche market, yes, but... (and you can give me a cut for these suggestions when you've made your dosh!).