No, not your check book, your MT audition book. As a voice teacher, my community of pedagogues and I have common stories of how some students come to us wanting to only sing a limited type of repertoire, because they've figured out what their type is, and they already book things successfully, so why deviate from what works?
While it's a good thing to know your type and what works for you, here are the top three arguments I've come across for diversifying your audition book. I'm curious if you've come across others, or if you are skeptical about some of these.
Many auditions continue to ask for contrasting styles or songs; this is especially necessary when auditioning for a repertory theater's season, but can still be the case for stand-alone shows here in New York City -- indeed many shows feature multiple styles of music within a single musical. This means if you're mainly a balladeer, you'd need uptempo songs; if you only sing in one style, you should have other styles in your book that you can pull out at relatively short notice. With jukebox musicals here to stay, and newer works that eschew a typical 'MT sound,' this also means balancing your MT rep with pop/rock/country/folk/R&B/rap. Balancing your book can help you book even more jobs.
Singing a range of styles helps to bring balance to your instrument. I've heard multiple Broadway singing teachers (e.g. Joan Lader) say their students 'sing everything,' not just one thing. What they mean is this: if you're in a show that keeps you chiefly in one resonance strategy, make sure you engage and continue to train the other parts of your voice. If you're singing belt-heavy repertoire, choose a song that has you going more into a light mix or head voice. Conversely, If you're in legit-mode for a bit, ease yourself out of the show by singing things where you're not only or chiefly in head voice. It helps keep you in balance; it helps prevent one mechanism from dominating, and your voice from getting stuck. Singers who already manage multiple styles well often attest to how they need a ramping up period in order to successfully move to another project requiring a significant style shift.
None of us wants to be one-trick ponies. Don't short-change yourself by pigeon-holing yourself into one type or style. Let those involved in casting do their job. Let's instead be in the business of embracing growth and the work and messy-ness that comes from continuing to grow our voices. And remember, your instrument changes with age as well (and so does your type, actually). Learning new styles and repertoire helps you to manage that change over time.
Some questions that can help you go down the path of finding a contrasting song:
If there's a singer you like, or an actor people tend to say you remind them of, what else has that actor sung? Dare to go down the YouTube rabbit hole and see the different genres they've attempted. Find that actor's resume, or BWW actor page and look at their body of work.
Consider the gateway song: even if a particular style might scare you a little, there's always a song on the periphery of the style that might beckon you down the less taken path. Dare to put on different playlists/stations on your streaming app and let serendipity lead you to something you might like.
As we all grow older, look a few steps ahead and find a song that you can see yourself singing in about 5-10 years from now. This can especially be useful for younger singers -- instead of limiting yourselves only to songs sung by kids your age, discuss with your teacher what 'adult' songs might be appropriate now, and in what key. Look at it as a longer term investment. (Word of caution: like the opera world, there is such a thing as doing a song for which one is not yet ready.)
Like most people, do you have more ballads in your book than you care to admit? Can you challenge yourself so that the next 3 songs you learn for yourself are NOT ballads?
Which of these MT style categories might you be missing? Broadway and pop standards of the 20s-40s; Golden age; post-golden age; Sondheim; Contemporary pop/rock and pop-rock musical; Mega Musical; Disney; Jukebox; Contemporary musicals with more traditional scores; non-theatrical pop/rock/R&B/rap/Gospel/Hip Hop; non-theatrical country/folk/bluegrass. Talk to your teacher if you need help delineating these categories.
If you love a particular composer / composer team, what contrasting songs have they written?
If your book has mostly songs that you can do in your sleep, what can you pick next that might be a bit more challenging? The converse can also be true: if your book is full of big sings, what repertoire can you look at that you can sing and not be worried about even if you've just rolled out of bed, or aren't feeling like you are in your best voice on audition day?
If your book showcases mostly songs that show-off your voice, what is a number that would require you to exercise your acting chops more? (And the reverse can also apply.)