Steve Jablonsky would be among the millions excited about the opening of “Transformers: Age of  Extinction” tomorrow if he weren’t so fatigued. “I barely know what day it is,” he says.  

Since last December, he has worked on the score for Michael Bay’s new “Transformers” film. He’s so tired, he’s not even sure how much music is in the film. “It’s about two hours of music,” he says. “We could figure it out, but we’re all too exhausted.” He has another algorithm: Working on one Michael Bay film is like “scoring two-and-a-half smaller films.”

He finished the score in early June, mere days before the movie debuted in Hong Kong. “Some people have told me not to mention how last minute it was, but at the premiere, Michael stood up and said, ‘I finished this film 40 hours ago.’ This one was the craziest film of them all.”

“Age of Extinction” is Jablonsky’s fourth “Transformers” film with Bay and his sixth Bay film overall. Part of the fun for “Extinction”  was finding themes for new characters in the reinvigorated story.  “Michael said to me, ‘This is new, let’s approach it as something new.’  I put aside all my old themes  and just started on brand new ideas. We have all these new characters: Mark Wahlberg, his daughter.  There’s a new villain, Lockdown. I focused a lot of time writing a theme for him. He was one of my favorites.”

Toward the end of the process, Bay and Jablonsky both had the same thought: they should incorporate a few of the original themes. “We thought the fans would like it,” Jablonsky says.

Bay brings Jablonsky, who was asked to join the Academy of Motion Pictures Arts & Sciences earlier today, in earlier than most composers start working on feature.  “There will only be a few scenes, because that’s all that’s been [edited]. He’ll call me and say, ‘Can you get down here?’ He’ll have scenes he’s excited about,” Jablonsky says. “It’s very much all consuming. There’s a lot of work from the beginning and it just gets worse and worse—maybe I should say better— it just intensifies. All these new images are coming in. Inevitably that means the picture is going to change and the music might not work. The score keeps changing as the film develops, but If I waited until the end to start, I would be dead. There’s no way I could do it.”

Also different for this installment of “Transformers”: Jablonsky worked closely with Imagine Dragons, who wrote the theme, “Battle Cry.”  In the past, Jablonsky had used parts of themes from Linkin Park and Goo Goo Dolls in his score, but this time, it “immediately hit me more than some of the previous ones had done.”  Bay suggested bringing the band to L.A. and then Jablonsky went to their Las Vegas studio and incorporated some of lead singer Dan Reynolds’ vocalizations into the score as well as his band mates’ music. “It was a much closer collaboration than I’ve had in the past.”

Though Bay has a reputation for being difficult, Jablonsky has found much to admire in working with the action king. “I wish people knew how smart he was. On a daily basis, he’ll impress me with the sheer knowledge of his entire film. He can play it back and forth in his entire head,” Jablonsky says. “He’ll say, ‘Remember that sound from that cue you did that you played me six weeks ago?’ He knows every little detail. It’s great to watch him operate. It’s still a pleasure for me to watch him create.He’s genuinely a good guy and a supportive guy and I think people generally think he’s a nut case and he’s not.”

After studying at University of California, Berkeley, Jablonsky got his start in the composing industry by cold calling Hans Zimmer’s Remote Control studio and asking if they needed interns. The answer was yes. From there, he quietly absorbed everything he could, watching Zimmer and his fellow composers, including Harry Gregson-Williams, work.  “Harry had just come over from London to set up his studio in Hans’ building and was looking for an assistant. I started working with him since I had some experience on the equipment,” Jablonsky says. “He’d let me mess around in his studio and I was scoring music to his films just for fun. He saw what I was doing and let me score a theme in one of his movies. Harry gave me that chance.”

Jablonsky, who also scored “Desperate Housewives,”  then started working more closely with Zimmer, from whom he learned things musically, but also how to navigate studio politics, a skill for which Zimmer is renown. “He is just great  at that,” Jablonsky says. “I just picked up a general vibe of how to handle yourself when these big-time producers and directors don’t like what you’re doing. Don’t freak out, just get into a conversation with them.”

Jablonsky, who admits he’s a little behind the curve on social media—he only joined Twitter a few months ago— says the feedback from “Transformers” fans on Facebook and Twitter buoys him. “It’s really amazing to see how many people from every part of the world have heard the music.  They’ll say they listen to it when they’re studying or exercising or they were sad and it made them feel better. I’m like, ‘Why didn’t I sign up for this sooner?’ Not because I need the affirmation, but because it gives it more meaning. I thought about them when I was working on the score. I’ve gotten message from soldiers from Iraq. It’s very touching.”