摘要：We saw the play separately and compared notes afterwards. (我们独自看了这出戏，然后交换了意见。) [牛津高级学者辞典]
compare notes的字面义是“对笔记”，引申义是“交换意见”，如
【例句1】We saw the play separately and compared notes afterwards. (我们独自看了这出戏，然后交换了意见。) [牛津高级学者辞典]
【例句2】We'd both been out with the same man at different points in our lives so it was interesting to compare notes. （我们在人生的不同阶段都曾与同一个人约会过，所以交换下看法很有趣。） [剑桥高级学者辞典]
【例句3】There's a camaraderie among regular commuters, and they compare notes and moan. (普通通勤者之间有一种同志情谊，他们互相交流、抱怨。) [柯林斯高级学者辞典]
用介词on补充信息，如
【例句4】Let's compare notes on our experiences. (来让我们交换一下人生体验。)[牛津高级学者辞典]
【例句5】The women were busily comparing notes on the queen's outfit. (女人们正忙着对女王衣着闲扯。) [柯林斯高级学者辞典]
【例句6】Leading scientists got together in Paris to compare notes on current research. （顶尖科学家齐聚巴黎，就当前的研究交换意见。） [朗文当代英语词典]
因为记的笔记常态不是一条，所交换的意见也是鸡零狗碎的多个点，所以note用复数notes。
来源：杰邦教育