But by the time astronomers had noticed it and set their instruments up to double-check, the signal had vanished.

但是等到天文学家发现并且使用仪器进行二次确认的时候它已经消失了。

Once connected to wires and set up, instruments such as a xylophone, drum or cymbal can play on their own.

只要通电并设置好，木琴、鼓或钹等乐器可自行演奏。