How we cite our quotes:
He was feeling a little mellow. It seemed a nice thing to him that they would give him a party. He played the Pavane to a Dead Princess and felt sentimental and a little sad. [ . . . ] When it was done he got another whiskey and he debated in his mind about the Brandenburg. That would snap him out of the sweet and sickly mood he was getting into. But what was wrong with the sweet and sickly mood? It was rather pleasant (29.42)
Doc is in a pretty weird mood during and after his party. He's happy, but also sentimental and sad, a funny mix of emotions. It's interesting that we learn about how Doc is feeling because he's trying to decide what music to listen to. Doc's mood and the music he listens to (either on the phonograph or in his head) are closely connected.