Advice on Writing Musicals, a critic's perspective

I went to see When The Clown Laughs by Joseph Traynor yesterday, I couldn't review it for The Skinny but I did offer up a couple of pages of feedback for the writer/director/co-star. I've made a more general digest for this blog as I think there's something valuable in it and I spose I should be making posts about what I'm doing as that's the whole point of having this blog.

• Be economical with your scripts. The common runtime of a musical at The King's is around 1h40 including interval! That’s about standard for a musical as that suits people’s attention spans. I certainly wouldn’t stretch to more than 2 hours all in.
  
  While scenes and songs are your children, you will generally find that making cuts of choice selections makes every line count and results in stronger writing overall. Especially look out for explanations that are repeated (does the audience already know this? Does putting this in add anything to the impact?)
  
  For songs, every one should add something to the plotline or have an important impact. They should not just serve to span things out. As a general rule if they do not contribute something significant that can specifically be named and justified they have to be cut. I’ve read about Stephen Sondheim writing over 30 songs for a show and leaving only about 22 of them in at the end, it’s just part of the process and no experience is wasted
  
  During scene dresses instrumental music should usually have some melodic material to it, not just the kind of music that accompanys someone singing. Without the vocal melody on top it sounds bare, it sounds like an accompanyment, which is what it is.
  
  Exercise caution in dealing with themes of incest (particularly in the first scene) as some people find this very distasteful. There are some taboos over being forceful on those issues in our society which can leave a bad taste in the mouth of theatre goers which certainly ought not to be an initial reaction.
  
  When actors have solos they should not be under-directed otherwise half way through the song they end up looking like a fish out of water, as though they don't really know what do do with themselves. Some action can be useful in keeping the audience's attention.
  Before you put a show into production do some work-shopping and ask other writers and theatre-makers to read your scripts or watch excerpts and comment on anything points that can be tweaked or any repetition that can be snipped to make the overall item stronger.
  Naturally all criticism is subjective, my only authority is that I see more than most people and write about it regularly.