顺便说

Could I just say in passing that … ?

我能顺便说一下…吗？

Incidentally, I think you still owe me some money.

顺便说一句, 我想你还欠我一些钱。

By the way, the music at this event was played by a man with a cittern, who not only performed with virtuosity, but also with a sense of humour.

顺便说一句，活动的音乐是被西特琴奏的，艺术，而且感觉上有些幽默。