We are playing the guitar.本句主要考察两点：

①现在进行时。

be＋doing现在进行时表示正在进行的动作，或者正在发生的状态。They are watching TV他们正在看电视。Lucy is eating Lunch露西在吃午饭。My family is having a noon break.我家人正在午休。

②英文"乐器"前要加定冠词“the”例如the piano, the guitar, the violin