下面的句子出版2019高考题的江苏卷：

It had excited within him the belief he could write one last song. 

疑问如下：

1. it 代替名词作形式主语吗？

2. one last song 是什么意思？一首最后的歌？好奇怪！

3. 全句怎么翻译？

附全文如下，供理解上下文参考：

The 65-year-old Steve Goodwin was found suffering from early Alzheimer’s（阿尔兹海默症）. He was losing his memory.

A software engineer by profession, Steve was a keen lover of the piano, and the only musician in his family. Music was his true passion, though he had never performed outside the family.

Melissa, his daughter, felt it more than worthwhile to save his music, to which she fell asleep each night when she was young. She thought about hiring a professional pianist to work with her father.

Naomi, Melissa’s best friend and a talented pianist, got to know about this and showed willingness to help.

“Why do this?” Steve wondered.

“Because she cares.” Melissa said.

Steve nodded, tear in eye.

Naomi drove to the Goodwin home. She told Steve she’d love to hear him play. Steve moved to the piano and sat at the bench, hands trembling as he gently placed his fingers on the keys.

Naomi put a small recorder near the piano. Starts and stops and mistakes. Long pauses, heart sinking. But Steve pressed on, playing for the first time in his life for a stranger.

“It was beautiful,” Naomi said after listening to the recording. “The music was worth saving.” Her responsibility, her privilege, would be to rescue it. The music was still in Steve Goodwin. It was hidden in rooms with doors about to be locked.

Naomi and Steve met every other week and spent hours together. He’d move his fingers clumsily on the piano, and then she’d take his place. He struggled to explain what he heard in his head. He stood by the piano, eyes closed, listening for the first time to his own work being played by someone else.

Steve and Naomi spoke in musical code: lines, beats, intervals, moving from the root to end a song in a new key. Steve heard it. All of it. He just couldn’t play it.

Working with Naomi did wonders for Steve. It had excited within him the belief he could write one last song. One day, Naomi received an email. Attached was a recording, a recording of loss and love, of the fight. Steve called it “Melancholy Flower.”

Naomi heard multiple stops and starts, Steve struggling, searching while his wife Joni called him “honey” and encouraged him. The task was so hard, and Steve, angry and upset, said he was quitting. Joni praised him, telling her husband this could be his signature piece.

Naomi managed to figure out 16 of Steve’s favorite, and most personal, songs. With Naomi’s help, the Goodwin family found a sound engineer to record Naomi playing Steve’s songs. Joni thought that would be the end. But it wasn’t.

    In the months leading up to the 2016 Oregon Repertory Singers Christmas concert, Naomi told the director she had a special one in mind: “Melancholy Flower.”

She told the director about her project with Steve. The director agreed to add it to the playing list. But Naomi would have to ask Steve’s permission. He considered it an honor.

After the concert, Naomi told the family that Steve’s music was beautiful and professional. It needed to be shared in public.

The family rented a former church in downtown Portland and scheduled a concert. By the day of the show, more than 300 people had said they would attend.

By then, Steve was having a hard time remembering the names of some of his friends. He knew the path his life was now taking. He told his family he was at peace.

Steve arrived and sat in the front row, surrounded by his family. The house lights faded. Naomi took the stage. Her fingers. His heart.