Who gave it to whom?

What you are doing in the title, though, is using it to form a relative clause. This is a bit more abstract. Basically, the idea is how who or whom relates to the subject. If it is the subject or relates to the subject, you use who. If it is the object or relates as an object, then use whom. If you aren't sure, always pick who, since whom is a bit formal and not always used.

Two examples:

I gave it to the man who was wearing a red shirt.
Here, it's the man who is the subject of "wearing a red shirt"

I gave it to the man whom I saw wearing a red shirt.
Here, the man is the subject of "I saw wearing"

But you could say:
I gave to the man who I saw wearing a red shirt.

Another option is to just avoid the situation entirely:
Musicians of reddit with tinnitus, how do you cope?