keyboard leaking black ink

I bought a used Yamaha keyboard and there seems to be some sort of black ink leaking out of it. What is this? What could be causing this?

It looks like ink. It stained the seats in my truck and couch at home. When I tried to clean it up it wouldn't come out. It doesn't appear to be an oil of some sort it really seems to be an ink. It's black. I can't figure out what is causing this or why it's happening. Has anyone else ever had this happen to them or know what's going on? It's a Yamaha keyboard I am no sure what model.