C-flat and B-sharp

Yes, they are real notes

This post is a continuation of my explainer on the difference between F-sharp and G-flat. To sum that one up: in our present-day standard tuning system, F-sharp and G-flat sound the same; the only difference between them is notational. In historical tuning systems, however, they sounded quite different. Tuning is hard!

In this post, I address the deeper mystery of the notes C-flat and B-sharp. Are these real notes?

In 12-TET, C-flat sounds the same as B, while B-sharp sounds the same as C. However, note names became standardized during a period in Western European history when tuning systems were based on just intonation, and in just intonation, all of these notes sound different from each other. Very different! C-flat is sharper than B, and B-sharp is flatter than C. Listen for yourself. Here's a chart.