Birds that sing at night?

Every night when I go to sleep I hear these birds singing in the middle
of the night. I know its not an owl or anything like that, it sounds like
a regular songbird that would normally sing during the day. The first
time I heard them I was kinda freaked out because I thought birds only
sang during the day. What kind of bird could this be and why does it
sing at night?

Well where are you? Country wise
Corncrakes, Nightjars and Nightingales are all migratory birds with a short and well defined song period during the spring and summer months. As well as the true nocturnal species, reed and sedge Warblers among others, sing extensively during the night.
This is in Britain.

Animal carer

It's a Nightingale hence the name, the breed sings at night.

Some birds like nightingales, whippoorwills, and owls naturally sing at night.

Take care.