I dreamt I was in some kind of hotel with many rooms and lots of people. Part of the hotel was a kind of hall with lots of bars and restaurants off of it, and in the middle there was a piano, but instead of the normal piano keyboard it had a weird grid of keys. A (very pretty) lady was playing the piano and singing and I watched for a while.
Some time later I somehow ended up with a slot at the piano, playing in front of the crowd, and I had to improvise a piece with piano backing and a sung melody. I sat down at the piano and looked at the weird grid of keys and pressed a few buttons, but I couldn't figure out how the notes worked. I tried playing notes together that were next to each other, and diagonal from each other. In the end I figured out how to play some chords, but I had no idea what they were!
The lady who was singing earlier came over and showed me a few things and then offered to sing the first song, so I improvised some chords and she sang over it. After a few minutes she left and I was on my own and basically made a fool of myself in front of everyone. Eventually I got up and left and everyone was looking at me.
I headed out to another part of the hotel and someone closed the door behind me. I was in a room with lots of people, and after a minute or two I realised this was someone's wedding reception. I tried to open the door to leave but it was lost.
I explored this part of the hotel, pushing through crowds of people and just trying to find a way out but the layout was confusing, like a labyrinth of small rooms and corridors. I woke up without ever managing to find my way out!