The theme song for “Steven Universe” is a whimsical, 30-second introduction to the complex but charismatic world of the Crystal Gems. It’s disarmingly charming, delightfully peculiar and perfectly captures the essence of the show.

Rebecca Sugar wrote it in her car.

“I was working on ‘Hotel Transylvania’ at the time,” explained Sugar, the creator of the fan-favorite Cartoon Network series. “I had these hourlong commutes out to Culver City from my place and I was writing it in the car.”

“Not the full, long version,” Sugar clarified. “Just the short, regular version.”

This rendition of “We Are the Crystal Gems” was the first song Sugar wrote for the show. And both versions are included in the “Steven Universe Soundtrack: Volume 1,” a 37-track digital album featuring songs from the show handpicked by Sugar and remastered by the show’s composers Aivi Tran and Steven “Surasshu” Velema.

The longer rendition of the title tune has a similar origin story: Sugar was inspired at the airport while traveling to a convention, coming up with lyrics even while taking her shoes off at security.

“I write all the songs on the side because I’m always busy working,” said Sugar.

The original music of “Steven Universe” is definitely a large part of the show’s appeal. Since its Friday release, the long-awaited soundtrack has peaked at No. 2 in overall album sales on iTunes (No. 1 among soundtracks), reached no. 1 on Google Play and No. 3 on Amazon.

The animated series stars Steven, a 14-year-old half-human, half-magic alien. Since the show’s 2013 debut, Steven, with his ukulele, has sung about everything from friendship to tasty snacks and even accidentally creating an alternate timeline. Although the show has gradually introduced heavier themes including identity, unhealthy relationships and overcoming loss — often via song — “Steven Universe” has retained its positivity and hope even as it further explores these uncertainties of growing up.

Sugar grew up playing the hammer dulcimer. Before switching to the “fun to play” ukulele as a teen she also dabbled a bit in piano.

“I got in trouble because I liked to change the classical music,” Sugar said. “I wanted to use the pedal on everything so it would sound pretty.”

While Sugar’s musical background also includes playing banjolele in “a loud band” while in college, she did not expect music to play such a large part in her career.

“[Music] was always something I did for fun. I never thought it would be part of my professional life as an animator,” said Sugar.

Sugar discussed the soundtrack, Steven’s journey and writing the show’s music over the phone.

What is the process for coming up with songs for the show?

The story always comes first. Actually, the feeling comes first. Sometimes I’ll be thinking of a song in the back of my mind that I want to write that is related to this feeling of a type of story that I’d like to write.

Oftentimes we’ll make an episode and build the story around that feeling I want to convey. And that will often dovetail with the kind of song I want to write.

But the story has to come first. It’s really important to me that all the songs in the show aren’t superfluous. They have to progress the story, and the characters have to change and have the need to sing them to change.

A lot of times I’ll try to figure out where I am when I’m writing the song and where I want to be when I’ve figured myself out. If I’m not there then hopefully by the time I’m done writing the song and working on the episode I’ve figured out why I wanted [to write it] in the first place.

Listen to "We Are the Crystal Gems" from "Steven Universe."

The songs themselves have evolved through the course of the show from ditties to those tackling heavier themes. How was that evolution for you?

The show was always designed to mature with Steven and with the characters and with the audience. I also went into that knowing that hopefully I will mature as a person. I started the show when I was 25 and I’ve grown up a lot too.

I’ve been trying to do things that are more and more complex as we build off of what we started.

I definitely couldn’t have written the songs that I’ve been writing lately when we started. That’s been the learning experience of the show.

I’m often partnering with [storyboard artist] Jeff Liu and [writer] Ben Levin on a lot of these songs and I’ve been so inspired by them.

I’ve gotten the chance to talk to Estelle [who voices the character Garnet] about what music she likes and her inspirations and what she thinks about the songs I’m preparing to write. That has been a huge influence on me. I also got to talk to Kate Micucci [who voices Sadie] about her songwriting theories.

I just learn so much from everyone. It fits really well because on the show Steven and all the characters have learned so much from each other too.

It’s really important to me that all the songs in the show ... aren’t superfluous. They have to progress the story, and the characters have to change. — Rebecca Sugar, creator of "Steven Universe"

Are there any songs that you recall that changed drastically from your initial feelings through the course of talking with your “Steven Universe” colleagues?

I had a lot of ideas for “Stronger Than You,” but it really wasn’t until I got to talk to Estelle about it that it set me in the right direction or just in a direction.

I was describing to her the episode. This was long, long, long before we even drew it, I was saying, “I need to write this song. Can I write this song? It’s a love song and a fight song and a victory song all at the same time. What would that even be?”

She had all these ideas and all these references and I just started playing them, putting them on loop, and thinking about everything she said.

The sound evolved so much from practicing and trying to live up to all the great advice she gave me.

Watch Garnet sing "Stronger Than You" on "Steven Universe."

You work with a lot of spectacular voice talent. Is it ever intimidating to write music for them?

Oh, yes. Oh, my gosh. I always ask in advance because I would never want to write a song for someone who doesn’t want to sing one of my songs.

I asked the incomparable Patti LuPone [who voices Yellow Diamond] if I could write her a song. When she said yes I could’ve fallen over. I did my best not to.

Writing a song for Kate Micucci, that was really exciting. I got to talk to her about that song a lot. She helped me so much.

I reached out to her because it was one of the first songs that wasn’t actually coming from the character’s emotional core. It’s a song that’s playing on the radio and I was like, “I don’t know if I know how to do that. I don’t know if I can just write this fluffy thing.”

I wanted to somehow have something in it that’s resonating. We were talking together about a fame scene and she had these thoughts about this ambiguous pop star character that has all the friends in the world, but there’s this fakeness to it. It was just great.

Watch Pearl sing "It's Over Isn't It" on "Steven Universe."

What was it like to be able to do an entire musical episode?

It was a dream come true. I’ve always dreamed of doing an animated musical. I love musicals. When we were finishing it my eyes were watering. I couldn’t contain myself.

It was so hard. There’s seven songs in 11 minutes. And I had so much help. There are songs by Ben Levin and Jeff Liu as well. We all chipped in and figured it out and Aivi and Surasshu were really involved early on. I got to collaborate with so many people.

“Don’t Cost Nothing” was me and Jeff, “Mr. Greg" was Jeff and Ben, “It’s Over” was me and Aivi. It was just so exciting.

“Both of You” is actually the first song I ever wrote on guitar, the song at the end.

Listen to "What's the Use of Feeling Blue?" from "Steven Universe."

Why do you think music is such an effective avenue to explore Steven’s growth?

There’s a quote from [Bob] Fosse — [he] talks about how if a character can’t express themselves enough through speaking then they should sing, and if that’s not enough then they should dance.

That theory really stuck with me, there’s just so much more nuance to how they’re feeling when they’re expressing themselves in that way.

And self-expression, that’s what it’s for. There are ways someone can say something, but when you sing it, there’s this depth. It only works with something that is heightened enough, or subtle enough, that you need to express it that way.

Needing to do [sing or dance] already tells you so much about how they feel.

Even the heavier themes explored in some of the songs are done in a positive way. How conscious are you of that aspect in your songwriting?

Very. Strive to create art that is moving you forward in your life, that is getting you further toward how you want to feel, where you want to go. Allow yourself to process feelings and learn about yourself as you’re making art.

I feel that way about cartoons. I feel that way about music.

All the characters of the show, and even the show itself is an expression of that.

There are always things going on and it’s hard not to feel defeated, but art is such a powerful tool to process those feelings and to shift them in your mind.

I was trying to do that with the songs on the show.

For “Here Comes a Thought,” I had been practicing mindful meditation and I was trying to figure out how to remember that myself, remember those tools.

With “It’s Over,” if you ever go through the experience of caring about someone so much, tying who you are to someone, and then losing that person, it can feel so impossible because you feel like you’ve lost yourself. How do you move through that? There’s a hope in it and there’s a beauty in the ambition to be beyond this place.

There’s always going to be something positive about self-expression. Even if you’re expressing something negative, you’re expressing it. You can then look at it. You can then process it. You can then accept it.

I’m a huge advocate for all forms of self-expression that doesn’t harm another human being.

Watch as Garnet and Stevonnie sing "Here Comes a Thought" on "Steven Universe."

What do you find most challenging about writing the music for the show?

It really varies from song to song. Some songs come out so easily. They’ll come out in one try or they’ll come out in one day.

Other songs I’ll be writing for months and months and I’ll do seven versions, and throw them all out. Then I’ll write something completely different and that’s what it will be.

Like “It’s Over,” I did a ton of versions of before I arrived at what’s in the show. “I Could Never Be Ready” I wrote in half an hour, 20 minutes, because I just had a feeling and it just felt like that.

It depends on how honest I’m being about why I’m writing whatever song I’m writing.

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tracy.brown@latimes.com

Twitter: @tracycbrown