zero pitch

例句：

1. 1. The music has a zero pitch, which makes it very soothing.
   这首歌的音调是零音调，非常舒缓。
2. 2. She played the piano with a zero pitch, making it sound like a grand piano.
   她用零音调弹奏钢琴，听起来像一架大钢琴。
3. 3. The singer's voice had a zero pitch, making it hard to distinguish between notes.
   歌手的声音是零音调，很难分辨出音符。