The Showtime series George & Tammy explores the complicated relationship of country music power couple George Jones (Oscar nominee Michael Shannon) and Tammy Wynette (Academy Award-winner Jessica Chastain), whose love story was troubled while their music was iconic. The “First Lady of Country Music” with the hugely successful song “Stand by Your Man” was a loving mother who was determined to keep going, no matter what life threw at her, and the once-in-a-lifetime voice known for “He Stopped Loving Her Today,” widely considered to be the greatest country song of all time, were always in sync on stage, even when their personal demons tore them apart.

During this interview with Collider, co-stars Chastain and Shannon talked about the pressure that comes with playing people’s idols, the 10 years that Chastain was attached to the project, taking on a song like “Stand By Your Man,” finding the voice of George Jones, where Tammy Wynette’s strength came from, the strange duck noise that Jones used to make, and when they were at their happiest.

Collider: You’ve both pretty consistently taken on challenging roles. Was this the most challenged you felt, or do you always feel like each role is the most challenging role while you’re doing it?

MICHAEL SHANNON: Well, I’ve played Elvis too, so I would have to, for a lot of reasons, at least equate this to that.

Image via Showtime

Fair and understandable.

SHANNON: On the one hand, there’s a lot of pressure, just because you’re dealing with people’s idols, when you’re playing a person that literally is revered by other people and other people have posters of them on their wall. And yeah, that’s a big responsibility, which can be alleviated by understanding that no matter what you do, you’re not gonna be exactly like that person. So then, all the stress of trying to do that evaporates once you reach that conclusion. But you can only come to that conclusion after you’ve done a lot of hard work and preparation.

Jessica, having been with this project as long as you were before finally shooting it, does it make it less nerve-wracking when you finally do it, or were you just nervous, no matter how long you had to prepare?

JESSICA CHASTAIN: Yeah, it’s actually even more nerve-wracking, right before you do it. Before, you’re doing the research, and I was attached to this for 10 years. It was just an idea. It’s not something tangible yet. So, we flew down to Nashville, and then, all of a sudden, it started to feel very real, and I started to get very scared about singing with a band. I’d never done that before, singing a song with musicians playing. I’ve done karaoke, but nothing like that. That’s real musician stuff. It felt, to me, like a huge leap into the unknown.

When the day came that you knew you had to do “Stand By Your Man,” what was that pressure like? Was it more nerve-wracking to take on a song that’s so famous, or were they all scary?

CHASTAIN: For sure, that was the most nerve-wracking for me. And we revisit it. We see it twice in the series, which I actually really like. Once was when it was being written, and there was another time when she was really performing it in Vegas. I like seeing the difference between the two because then it’s not just about, “Okay, how do I make the song sound the best it can sound?” It’s more about, “All right, how do I show what Tammy’s going through, in this moment, and express it through her delivery of this song, so it doesn’t feel like I’m trying to copy a recording or a certain performance by her? I just wanted it to feel like I was trying to tell the story through the music. That, for me, was the way in.

Image via Showtime

Michael, how did you approach finding the music of George Jones? Was it about the overall tone and feel of the music? How did you find your voice in his voice?

SHANNON: Well, there’s a lot going on in his voice. One of the things he was most known for, I’ve heard people refer to it as licks. He does these licks, where he’ll take a note that would traditionally just be one note, and then he adds a bunch of notes onto it, towards the end, fluttering out of it, up and down, and all over the place. That was one of his signature moves. In a weird way, it’s got a jazz thing to it. It reminds me of scat singing. That was one of his trademark things.

And then, the way he actually held his face when he sang, his mouth never opened up that far. He always looked like he was almost trying to keep it from coming out, which I always thought was really interesting form, but in the process, created a really full sound. That’s something that our vocal coach, Ron Browning, helped me explore how to do.

Jessica, from Don Chapel to George Jones to George Richey, Tammy Wynette put up with a lot from men that she shouldn’t have ever had to put up with. Where do you think her strength came from, to keep going on for herself and for her family? She just seemed to keep barreling through, no matter what.

CHASTAIN: She knew she had a God-given talent, and I do believe that George Jones was her equal in that. Even though she was married to other people and had a lot of difficult things she had to overcome, music, in some sense, was something that made her feel whole and made her feel seen and understood, especially when she was singing with George. When you know you have something that you have to express, it keeps you moving forward.

Michael, what was it like to do the duck noises? Did that ever feel bizarre to do, or did it feel like a bit of an emotional crutch for him?

SHANNON: It’s certainly fascinating how it came to be. That was a very dark point in his life, perhaps the lowest point in his life. To be making cartoon duck noises, when you’re in as much pain as you’ve probably ever been in your life, it’s pretty ironic. There was also another voice he would do that we didn’t really use in the show so much, which was the old man. The duck and the old man would get in arguments with one another. I don’t think I ever did the old man voice. I guess it’s because my regular voice sounds so much like an old man that they thought people wouldn’t know the difference. Our assistant director was really good at making duck noises, and he used to taunt me with it. He would do them all the time. It was so easy for him, and it really made me hate him.

Image via Showtime

Jessica, there’s a moment in the series, toward the end, where George asks Tammy if she’s happy, and no matter what lies either of them are telling the world or each other or themselves, it’s really obvious, in that moment, that neither of them is happy. When do you think it was that Tammy was really actually at her happiest?

CHASTAIN: It depends on, at what point in your life. Certain things make you happy at one point that may not make you happy later. For sure, she loved her kids. She loved being a mom, and cooking for them and making a meal. I know she also loved performing and singing a song. Being in the kitchen cooking and taking care of her family, and then also being able to sing were the things that really gave her great joy.

Michael, do you think that George understood that feeling of happiness, because it seems like he just ran from it, every time he realized that he might be happy?

SHANNON: I don’t know. I’ve seen a lot of pictures of George, and the pictures of George that I’ve seen where he looks the happiest is when he’s at home with the kids, just goofing around. That’s when he seems genuinely happy, as much as you can tell from a picture. And apparently, when you talk to Tammy’s daughters, that she had before George, they all say that they loved having George around the house and that they don’t have any issues with him, whatsoever.

So, I really do think he was happy there. But it was a lot of pressure on these people. It was not just them and their desires. There were a lot of people around them that, as we’re showing in the show, wanted things from them, and wanted them to keep doing what they did because a lot of people were benefiting from it. You don’t always get to just stay at home because that’s what you want to do.

George & Tammy airs on Sunday nights on Showtime, and is available on-demand and streaming.