Just one week into the " American Idol" finals season and already the first shock waves spread across the Idoldome; not really for the ouster of rocker girl Amanda Overmyer, a delightful personality but ultimately an underperforming novelty candidate more than a serious contender. Far more shocking was the first intimation of many heartbreaks to come with the horrifying placement of the Great Irish Hope, Carly Smithson, in the bottom three.

With nine weeks ahead between now and the finals at Nokia, there will be surprises aplenty, and all but two of our warriors must fall before that day. In a season as rich with competitors as this, no one, it seems, can afford even one off week (no one except the Chosen One, David Archuleta). There were, however, some heart-stopping moments while we in the Idoldome watched a stricken Carly wait to hear her fate, and there is good reason to think a major riot would have ensued had the verdict gone another way. As is, we can chalk this up to one of those helpful early scares many go through and that can motivate a singer's partisans.

Last week, I had a fascinating phone call with one of the people most responsible for helping the contestants to avoid a bad week: Debra Byrd, "American Idol's" vocal coach and arranger.

I expressed to her my sympathy for the contestants in the ridiculously impossible task of picking (in one day) a song that allows them to express their vocal abilities but also stays within their natural range, that shows they can do something different while being true to the original version, and that shows they can pick a great song, but not one whose original version is so great that you can't possibly touch it.

Offering a case study of how she helps them navigate this, Byrd shared the back story of what has been perhaps the most celebrated performance of the season: Chikezie's rendition of "She's a Woman."

"What you did not see was the agony of him trying to choose the song. He had chosen 'Help!' and we worked on it and he began changing the arrangement. He changed the chords. And I said, 'You can't do that to a Beatles song, my dear. Sorry.' And I said, 'You're going to have to do one of two things. You're going to have to surrender to what the song is or you're going to have to pick another song.' " Late in the game, with only a tiny amount of time left before the Tuesday show, Chikezie "slept on it, thought about it overnight and came in and said, 'OK, I've changed my song.' "

Byrd continues, "When he first sang the song 'She's a Woman,' I couldn't feel it. I said, because part of it is finding it, 'Is it an R&B vibe? Is it a rock vibe?' How do you see yourself singing it?' And he got very excited and he said, 'Oh, OK! I want a banjo and I want a fiddle!' And I was like, OK, now I can hear it. And as soon as he said banjo and fiddle, then I could hear it."

On last week's other major sensation, Smithson's "Come Together," Byrd revealed that although she had performed this frequently before, the rehearsal time also brought some critical changes. After practicing it a few times, Byrd and Smithson felt that despite the singer's comfort and history with the material, something still wasn't clicking. It was at this point that Byrd wondered, "With her band was she singing 'Come Together' in Paul McCartney's key?"

"She sang it and I said, 'No, no, no. Let's try another key.' We changed it to a higher key. And you know she was very happy because it changed her vibe. She didn't sound like a guy anymore. She sounded sexy like Tina Turner."

One of the biggest challenges, as the judges complain and Byrd commiserates, is working with contestants to find their musical identity. Although some arrive fully formed, for others it's a grueling process that may not sort itself out until late in the season.

"They have to discover themselves," Byrd said. "And what we on the music team do is, we help them discover."

richard.rushfield @latimes.com