Around the 0:21 mark, there is a piece of music which appears in the Looney Tunes short called What’s Opera Doc.

I'm curious to know if it's an actual piece of music or just warm up.

https://www.dailymotion.com/video/x2p7pt3

That little stretch is supposed to mimic an orchestra tuning up. The actual music starts around 0:40.

Thanks. I wasn't sure if it was an actual piece of music or not, so just wanted to ask.