I enjoy singing, but I don't think I could do it a cappella style, without musical instrument accompaniment in the background.
Yeah, a cappella seems like since your voice is the only thing making sound, there is nothing to hide behind if you are off key!
Yes, and I need to hide the fact that I am a poor vocalist behind very loud music, especially when I'm in my car, lol.
Ha!  Very true for me as well.  When was a capella created and popular?
It's definitely got its origins in religion, with Chinese opera, Hindustani music, and other forms of gospels and hymns. Unsurprising, right?
That makes sense.  So, it has been around for a really long time then, right?  Are there any famous a capella singers I may know?
Absolutely! Rockapella is probably the most famous one, but there's also Pentatonix and Home Free, all really amazing at what they do.
Oh yeah, I have heard of Pentatonix.  That seems like a very niche skill though.  I wonder if it pays well.  
I mean, Pentatonix won "The Sing-Off" season three and caught 200 grand for it, so I'd definitely say there's some opportunity there!