Here's how I would do it:

The first step is to create the story and make sure that it would work as a musical. You make an outline and make sure you have all the elements of a normal story.

Develop your characters. What's their personality? What kind of songs do you picture them singing? What kind of bond or dynamic do they have with the other characters?

Figure out an approximate number of songs you would want. Figure out what characters would sing what songs.

Write the script. This can help to build the story and provide something to help write the songs on.

Then you can go through the outline or storyboard and mark where you want all of the songs.

Then start writing the songs. You can do it by yourself or collaborate with someone else.

Then, get a group together to read the script and sing the songs. See how it works. Then, rewrite as necessary.

And I mean after that, you dive into the production side of things, and idk how that would work.

This is based on nothing but my own experience, which is not much. I like to write, especially scripts, in my free time. I've experimented with writing musicals and have never gotten very far. So take all of this with a grain of salt. But I think this could help you get to a starting point. The most important thing is to try, even if it doesn't work out. Just try. You never know what could happen.

There's a sub r/musicalwriting that might be more helpful but everything I've seen in the comments is good advice

I wrote one and it sucks, but I think I sort of got the hang of it. I think the key is figuring out how to make the story compelling, and leaving good spots for songs that move the plot forward. Make sure you figure out the characters and their motivations or it won’t make sense why they do stuff! Hope this helps.

One note at time.

I come to musical theater from an odd angle - I improvise musicals regularly with a live accompanist and a cast of 4-8 vocalists.

I don't have much insight into writing them, but the best (for my money) musical improvisers - the cast of Off Book - is documenting their process of scripting a musical on their podcast feed. If you look for Off Book and then find episodes labeled "On Book" you'll find them. Might be insightful? But also their process might not match what works for you.

David Spencer, in The Musical Theatre Writers Survival Guide says that “songs eat book”. In other words that you should come up with the plot and dialogue first, and then find moments to replace with song. I personally am a believer that you should write the part that is most exciting to you first.

Journalist: “Mr Sondheim, is it lyrics or music first?”

Sondheim: “The book.”

If you have an idea for a story, try making a loose outline. Don’t worry, it will change. Fill in spots where you have a strong idea for a specific scene or song. And keep filling it in. It’s ok to have big gaps. Then, just like a sudoku or a crossword puzzle, work on what you can based on parts you can connect. Whether that’s a song or dialogue.

Generally, the contract.

One song

Glory

Some people do all three: see Dave Malloy and The Great Comet.

Some people write music and lyrics and partner with someone for the book: Sondheim and James Lapine for Sunday in the Park with George.

Some people write the music and have a partner who does the lyrics and a third person writes the book: Jule Styne, Sondheim and Arthur Laurents for Gypsy.

Other variations exist: Oklahoma! where Oscar Hammerstein did the book and lyrics and Richard Rodgers wrote the music.

Think of the book as the plot and dialogue and how they are presented. The Great Comet had essentially no dialogue and was based on a 90 page section of War and Peace, but somebody had to decide what was left out and how the songs flowed into one another.

The book (or libretto) is the story, the plot and dialogue and stage directions and all that.  Think of it as the actual play without the music.   

The lyrics is simply that - lyrics for the song and they are usually in CAPS in the libretto.   

Basically the playwright writes the book.   The songwriter/lyricist writes the lyrics to the songs.  

Book is the story and dialogue - it gives shape to the musical

Depends on the musical. For something like Mufasa (not a traditional theatre musical but stay with me), Lin Manuel Miranda received a script and found places where he thought a song would fit well and wrote them. Other teams it’s a more collaborative process, where one person might have the story but not necessarily the literary skills to write a book. Or the music but not a plot. Or the music but not the lyrics (see West Side Story).

Not everyone is capable of doing everything themselves or are much better at one side of things than another.

The book is the structure of the story... Regardless of whether there is spoken dialogue

The book refers to the story beats, plot, and structure. The bookwriter will also contribute dialogue to the musical. It's the bookwriter's job to make sure that the story is being told through song and that can be a more difficult burden with more sungthrough material

Fine question, since it's a bit of semantics too.

From a credit standpoint, the credited author (Book by) of same is creating the completed script - and takes credit for play and scene construction, all staging and physical action description and character dialog. As said elsewhere here, much like a playwright who writes a play script sans lyrics. A libretto is this product, but contains the music and song cue instructions and lyric and some book writers are librettists and some are not - it depends chiefly on whether they cover book and lyric.

In the best partnerships, composer, lyricist and playwright would work closely together to develop the show's overall structure, at least through a comprehensive outline stage (beats and actions.) This assures that all partners contribute ideas, come to mutual agreement and proceed to replace sections of the play's action and dialog, with song in a way that provides maximum plot function and moves the story forward in real time.

This also means that while credit is taken by the book author, the actual outline development is by all partners - uncredited by mutual agreement. In fairness, this sort of cross-over works well in all disciplines: the lyricist may provide much useful input on music form and style to the composer, the book writer may provide outstanding lyric subject and ideas to the lyricist. And, in turn, this symbiosis assures that all partners equally understand the mechanics and intentions of the project - what collectively they mean to achieve. Composers, by example, (and I am one) who sit outside these discussions or decisions and simply set the lyrics they are handed, earn all the failure the show gets. Their chosen ignorance of the decisions that took the show off-course are entirely theirs: they could have, should have taken greater interest in those poor choices and decisions as they were being made. It only takes one partner to see a potential problem and bring it to the attention of the others. But, no attention to these things increases the chance of error.

There are many autobiographies written in the subject, plenty form playwrights who are book partners for musical plays. These can give you a very specific understanding how the division of labor and creation is assigned within that partnership, on that project.

Book/ Libretto = Script and lyrics. No musical notation i.e composition , sheet music etc. Check out library etc for some examples of major musicals books for examples of what are included. Good luck!!!

I think of the “book” as a fully written play, just missing the music.

The book is the script and/or structure. It's not an actual book.

Frankly, it sounds like you've put the horse before the cart. And with 45 songs, that's a really big horse!

You say you have no collaborators. How do you know if the 45 songs or the 160 pages of material are any good? Long before contacting a producer, you need to test the product. I can tell you right now, 45 songs is waaaaaaaay too many songs. It's just not within human dimensions for a night of theater!

Musicals aren't written. They're developed and rewritten and re-worked and rewritten . . . so you will need collaborators! Readings, sing-throughs, workshops -- these all require collaboration. It's through this process that your work becomes stage-worthy and also establishes itself as a possible production for, say a community theater or a regional theater. Unless you have a very rich uncle, that's the only road to Broadway. Someone has to see it as a viable product.

I always say -- you finished writing your musical, so now you can get started!

You have songs and scenes, but so what? A beautiful song, sung in the wrong place, will be an unwelcomed intrusion. A big flashy dance number may seem like a good idea on paper, but on stage, it may become an anchor, weighing down the momentum of the plot. You may have very well-written, funny scenes that prove to be too long -- -- or that fail to get laughs -- or that just don't play.

These are the sorts of things you can't know until you actually start turning your recipe into food that can be served. I'd say, don't worry about finding a producer. Producers will come find you when they see a great product. Focus on the product.

Have you done a table read yet? That’s usually beneficial before a professional workshop. 

Building up to get an agent/producer is a long process. Put yourself out there, but be patient. There will be many a rewrite and rework in between.

Starting the next script is always an option as well. 

You don’t need an agent unless you have any upcoming deals or contracts you need to sign. Agents only sign up writers who are bringing in money.

Your work is automatically protected nowadays, as you have a digital record of when you saved the file etc.

You don’t need a lawyer but you can join a writers’ union and they can usually provide legal advice when needed.

You need to get your work noticed by producers. There are lots of ways you can do this:

• Emailing your work to producers (terrible idea, only works once in a blue moon)
• Entering competitions (works better, but your writing has to be at a very high industry standard)
• Taking part in showcases (you have to pitch your work to showcase producers)
• Producing a short run of your show in a festival (really great if you have the money… otherwise you need friends who will perform for you for free)
• Creating a social media presence for yourself (very hard work, kind of mandatory, very low returns, soul-sucking… but costs nothing)
• Open mic nights (can be fun, community building, you’ll make friends)

Wishing you the best of luck!

Ultimately, you need to get the work on its feet with top-tier talent to get recognized by producers. I attended a concert reading (next to no book, more so songs) of a musical by a composer acquaintance (former student of my voice teacher; coincidentally the son of my high school music theory teacher) last year. It was at the Cutting Room in NYC and featured some strong talent (my voice teacher also attended a workshop the year before that had more book scenes) From The Cutting Room, they got a producer interested -- which was the main purpose. This year, they did another workshop/reading, with even more top-tier talent -- Tony Yazbeck, Robert Cuccioli, Kate Rockwell. That was very recent and it sold out. They're on a multi-year track of getting their musical recognized at higher and higher thresholds. But, it starts with you being your own advocate for your show and getting it on its feet one way or the other the way you intend so others can latch on to your vision.

Other things to do -- get a director on board to help shape the show. They know producers and they know theatres, so you can build up a resume of productions critics and producers can go to. Submit to festivals (not contests) where others produce it for you so you can gain more developmental experience. It's not enough for your Broadway friends to listen to your material. They need to sing it! They need to share on social media, get fans excited, etc. Capable performers always want new material that fits them like a glove and they'll help you learn more about the voices that can sing the material. Audra McDonald recording How Glory Goes from Guettel's Floyd Collins gave that show a lot of awareness. You also haven't mentioned yet, but you should have a website or some way to digitally display your demos, synopsis, etc. You mention potential talks with a big-time producer -- lesser known ones hungry for a win might be a more likely advocate for your show and willing to take an unknown writer on. You can also start making connections with casting directors to assist you in realizing your work.

Addressing the elephant in the room -- 45 songs is too many. A show that runs 3 hours is a major no-no. After intermission, strong chance of paying overtime to musicians. You're not Les Mis...yet...you can't treat yourself like you are (and Hamilton is sung-through and Lin-Manuel Miranda was already a Broadway talent before this). No producer will take on an unknown writer who intends to blow the budget before previews are done. YOU need to cut your show down -- don't wait for others to because they'll pass on the long version and never get to see what it could be. That's why your next step should be getting a director on board to collaborate with you in guiding the work toward what it could be.

Why not get the songs on Youtube in the sequence they would appear in the musical and see what response you get ?

Stephen Schwartz's Seven Questions are a good way of approaching the basics.

1. What is it about? What are the themes of the show? What does your story say about the world?
2. Why should the audience care? Why is this an important story to tell?
3. Who should you root for? Who is the 'Hero?'
4. What do they want? If you know what a character wants, clearly enough, you're bound to start rooting for them.
5. What is keeping them from getting it? What is the obstacle that they have to overcome, in the plot?
6. Why do they want it? It's important to have a specific 'what' that the character wants, but also a deeper 'why'.
7. "When do I get to go home?" - What is the natural end to the story? Does the hero get what they want? Does the hero get what they deserve? Does the hero change so much that what they want changes too?

This is just a starting list of questions, but it really does get to the heart of writing stories. And it's this kind of clarity that musicals really thrive on. The answers to these questions will start to land song ideas into your lap

Try looking through your plot, listing out the elements, and figuring out where your songs would fit. Figure out what kinds of feelings those songs illicit and what they serve to the plot. That should help you to get a general vibe as to what your song might sound like. From there, maybe do a scene breakdown, that tells you what things would actually be in each scene, and that should help with actually writing the book. I’m sure from there you’ll have a strong enough skeletal system to work out what needs done. If you play piano I’d recommend messing around there just to see what kinds of sounds you like for certain feelings, maybe. Watch plenty of videos, don’t be afraid to use your resources (good you’re already here lol). Take my advice with a grain of salt, I’m just a beginner here.

Please for the love of god whatever you do just don’t use AI.

Get a white board. Make into sections

TO DO IN PROGRESS COMPLETED

Then a smaller one

TODAY:

TO DO COMPLETED

Writing a musical is like filling out a crossword puzzle. It doesn't necessarily matter which part you fill out first because it'll lead you to another part. And just like a crossword puzzle, if your first answer is wrong, that will influence more parts of it to be wrong until you start figuring out more and more right answers. As for me (I've written 8 musicals, 2 of them played Off-Broadway), I think a great place to start is not just your plot but an outline. What happens in each scene? What song happens in that scene and what is the general vibe of it? You don't want four ballads in a row, but four patter songs or uptempos in a row can get old too. Find preexisting musicals kind of like the one you want to write and figure out their structure. A good rule of thumb is to have 7-10 scenes in Act One, 5-7 in Act Two. Typically the song in each scene should either be the one that contains the most potent emotional moment in the scene (joy, anger, argument, etc.) or the most important information in the scene (who a character is, what they want, how they attempt to get it, etc). In as many songs as possible, try to either move the plot along (take us from point A to point B) or explain something that is important for the audience to know. Read Jack Viertel's book The Secret Life of the American Musical (or listen to the audiobook, which I prefer), that will give you a great idea of how to pick which song goes where. Another way to start would be writing songs for the most important moments in your show. That can help you figure out what tone and style you're going for (or *not* going for). And finally, do not attempt to reinvent the wheel. Writing a great musical is hard enough already, but doing something that has never been done before is about as likely as an archer firing an arrow and splitting the one that's already stuck in the bullseye; you don't yet have the experience to do it with expertise, and you're almost definitely not gonna do it with luck. Stick to established structures that have worked before and trust that you can pour your own unique work into them. Good luck to you.

The best advice is to build yourself a team of a few dedicated collaborators who share your passion for the project. Now that you’ve poured your all into this draft, you have thoroughly accquainted yourself with the material and your story and slowly your blind spots will start to become more and more apparent. Having collaborators, in this case probably best to start with a composer, is going to get eyes on your work and bring out points and things that you never would have thought twice about, but could likely be improved upon through collaborative work.

Once you’ve assembled a team (can literally be one or two other people) then you can all put your heads (and time) together to make something happen with the piece. Submit to festivals, organize a reading with local performers, shop it around to schools and community theatres. Get people who do shows, on and off stage, to look at and listen to your show. Thats the tried and true way to make headway.

This community is a great place to start when looking for collaborators (a process we are working to formalize further), so have at it and get to work! It truly is never finished, even once its premiered.

Firstly: big ups on finishing a show!

The main issue you're going to have is that there's not much that can be done with a musical that's longer than 10-15 minutes (suitable for ten-minute play festivals) but shorter than 80-90 minutes (long enough to be produced on its own). You might want to think about writing companion pieces that use the same/similar forces and turning them into a program of one-acts.

Hey! I'm in a similar boat as you (well, I'm also a musician so I do have demos and full songs.) So I can't offer you too much advice but I'm very interested in answers.

Anyway first big question is "what do YOU want from your show?" Staged production? Recording? Someone to pay you for it? What in your mind's eye is the end of the line for your work? Because it could very well be that with your script done you're simply ready to move on to the next project and shelve this one.

For me it took a long time to decide on the answer to that question, but considering everything in my life and work together, I decided I'd give it a table read with an audience and probably shelve it after that. I strongly believe that theatre must be performed, and must be seen and heard. It doesn't really "exist" as theatre until that happens, as our art form is a means of expressing ideas from creator to audience. The expression is the end. You may feel differently!

if you can't get anyone to help you, make tracks online with things like garage band, I dunno.

I’d be happy to work with you to get this project finished—writing out sheet music, composing accompaniment parts, preparing demo tracks, or whatever might be helpful. I just graduated with my bachelor’s degree in music composition and I am experienced with musical theatre writing (including but not limited to lyric/text-setting, vocal arrangement, writing accompaniments, and orchestration). Feel free to DM me and we can discuss the project, budget, timeline, etc.

I mean musicals have the benefit of spectacle, of (hopefully) catchy songs, of (again, hopefully) thrilling live performances. It's hard for any source material to compare. At the same time, novels have the benefit or length and of really staying with the characters. You used Les Miz as an example, which I find a fascinating contrast because I think both the musical and the source material are frankly spectacular but in extremely different ways. The book is a labyrinth of characters and intrigue and it frankly takes a while to get going but once you're hooked, buckle up.

I will say your question ignores many of the UNSUCCESSFUL literary adaptations: "Pipe Dream", "Breakfast at Tiffany's", or "Carrie". It's easy to make generalizations when you're only looking at the successes.

I fundamentally disagree with the premise. The fact that musicals are based on literary classics is irrelevant. The audience is responding to performance. If you want a direct comparison, have an audience sit read the libretto or script! It’s not what you do, it’s the way you do it, imo.

Actually, they don’t. The opposite is true. What you are doing here is cherry-picking the rare exceptions and declaring they are typical. But if you were to list all the musicalizations that have been done on a literary property, you would find that the vast majority of them failed and have been forgotten. Very few are successful, and even fewer endure as literature in their own right.

This is known as Survivorship Bias - only looking at the successful examples and ignoring or forgetting about the failures. For example, when a Tony winner clutches their statue and emotionally proclaims “This proves that dreams can come true if you never give up!”, they are basing that only on their experience of winning and not taking into account the thousands of young actors who study and get degrees and keep auditioning, but never get jobs and have to leave the business to survive or feed their families.

If you are really interested in getting the answer to this question, you would need to find a source that could tell you, say, every musical that opened in New York in last 50 years, what was the source material, and then summarize the success of the source material vs. the musical.

I think most people who see musicals do not know the original work.

"Let's just say it's a Saturday night and you want to go out on the town;

Got a lady to flatter who might give it up if you don't let her down;

You could go see a tragedy...but that wouldn't be very fun.

Or a play from Greek mythology...see a mother have sex with her son. Blech!

You could go see a drama...with all that trauma and pain;

Or something more relaxing, and less taxing, on the brain.

Go. See. A. Musical!"

-Something Rotten

Most obviously, Oklahoma! for integrating the songs and the story.

More recently, Hair for using the rock idiom, Jesus Christ Superstar for the through-composed style, and In The Heights for Latin and rap music.

I feel like this is a loaded question that could honestly even be broken down by genres. While I’m the biggest RENThead, I could go on about various shows that influenced RENT and Jonathan Larson. I mean obviously there’s a show every few years that stands out or rocks the boat, but still a question with many, many answers

I would say Rent and a more contemporary one would be Hamilton.

Show Boat.

Oklahoma, Hair and JCS for rock music, Company and Chorus Line for concept musicals, whichever 1980s British megamusical came first, Rent. And nobody likes this answer including me but Mamma Mia and Jersey Boys opened the floodgates to the million jukebox and bio musicals we see now.