sing flat

• 把调子唱低了；以降半音唱

sing flat的用法和样例：

例句

1. Please ask the singer to pitch the song up a little,they sound rather flat.
   请歌手把调子唱高一点，他们唱的调子太低了点。
2. When she is nervous, she can't sing flat notes.
   她紧张时唱不出降半音的调。
3. I can tell the difference between a flat and a double flat notation.
   我可以分别降半音符号与双倍降半音符号之间的区别。