Q: A lot of people think your interpretation of Jeff Buckley's version of "Hallelujah" was your best performance.

Castro: I don't think it was my best vocally, but I felt it was a good delivery. That's one of my favorite songs of all time. Eighties week was tough. There's a lot of good rock, but I'm not a rock guy, at least singing-wise. I used to be the rock guy, and now I'm like this mellow singing guy. I was actually going to do a Dan Fogelberg song originally that we had a hard time clearing. I had to consider other songs, and then I stumbled upon (the fact) that "Hallelujah" was originally written and released in the '80s. I had known the (1995) Jeff Buckley version, and I knew Leonard Cohen had originally written it, but I never knew the date. It's a special song. So many people hadn't heard it, and I'm glad now they have.

Q: What has working with this season's mentors been like?

Castro: It has been awkward. I mean, meeting people in general, usually I'm cool, but the situations are just so weird. You're about to sing their song, and you don't really know it yet. But it's been really cool. It's probably more challenging than stepping onstage. So it's a growing process, making you stronger. Even if you're freaked out and you don't think you can do it, you have no choice. You have to do it anyway and make a TV show out of it. It's all confidence-building.

Q: Have you felt like you've been in a bubble while competing on "American Idol?"

Castro: Oh, sure, but I guess it's necessary. You could not do this any other way than being isolated and focused. I rarely go out, but I sometimes I go to dinner with my family. You hear people whispering and talking and everyone wants to take your picture. And autographs are awkward. Don't ask for autographs, people. I don't understand the whole autograph thing. I don't know why people like my chicken scratch. It's strange.

Q: Is your family musical? When did you realize you could sing?

Castro: My whole family is musical, starting with my grandfather on my dad's side. He was making his way to Mexico City to make an album when he met my grandma in Colombia, and he ended up settling there and having eight kids. I have five uncles, and they all play guitar and sing. Any time the family is together, they pull out guitars and start singing, so I was always around it. But I never sang.

I grew up playing drums, and I never would sing, just because singing is such a vulnerable thing. If you're playing an instrument, you can mess up and it's like, "Oops," but if you're singing, it's like your voice, you know, and it's just intimidating to me, so I never (sang) until a few years ago.

Q: How did you decide to audition for "American Idol"?

Castro: Well, it took a while (for me to start singing). Still to this day I'm not that confident. I had a little recording setup, and I started recording myself. For a good year, I hated everything I recorded, vocally at least. And then I started showing some of my friends, and once I started getting the (reaction) "Wow," I was like, "Ooh, maybe I'm singing well." Last summer, I thought, "I'll show my parents, see what they think," and that was scary. And they couldn't believe it. They said, "We always knew it," because they always begged me to sing. That it was about the time the commercials were going on TV for the "American Idol" tryouts and they said, "Why don't you go do that?" My dad went with me, and that first audition was the scariest because I (had) performed (only) about five times in public before the first audition.

Q: It seems like you've developed a large fan base. Do you hear from them a lot?

Castro: I can't even wrap my head around it. There are people that love me and support me, and it's so weird knowing I could put out an album and they would buy it. It is just crazy. I think I have the best fans because every day I get more letters than everybody. More postcards, more packages. I have a life-size plush panther in my room. I got fruit baskets and 150 balloons yesterday because they heard I was sick. They show me a lot of love, and it's really cool.

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