Welcome to Crash Course Music, a series where we break down the how and why of music! In this series, I'll be discussing how we musicians like to think about musical concepts, how those concepts came to be, and what you can do with them. _____WHAT TO EXPECT_____ My basic plan for the series will have five main parts. The first part will provide a framework for the concept of musical intervals in the first place, and explain why some note combinations are perceived as consonant while others are not. The second will discuss Diatonic Scale, one of the most common and most important musical scales in nearly every tradition around the world. The third will explain how nearly all modern music is out of tune, and why musicians might actually want it to be that way. The fourth will discuss the written language musicians use to record and describe music on paper - especially the naming schemes we use for chords. After that, I will be making a number of deep dives into non-diatonic scales, including Augmented, Diminished, Melodic Minor, Hijazkar, Rast, and more.