be busy preparing their performances
...watch his deskmate beating the drums 看他的同桌在敲鼓 be busy preparing their performances 忙于为他们的节目做准备 practise singing practice n. sing-sang-sung （practise doing sth） 练习唱歌 .
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be busy preparing their performances
忙着准备他们的演出
以上为机器翻译结果，长、整句建议使用 人工翻译 。