I've been making electronic music for the past year but recently decided that I need to sit down and learn some actual theory. So, I picked up a copy of Guide to the Practical Study of Harmony by Tchaikovsky and I had a quick question about how he's describing major/pure intervals.
Thus, we learn, that a major or a pure interval is converted into a minor, diminished or augmented interval by lowering or raising the upper tone...
In this passage, and a few others in the introduction, he seems to be using Major and Pure interchangeably in his sentence.
So, I'm just looking for clarification here, are Major and Pure intervals the same thing? Or, I suppose this is possible, that the rule he's describing just applies to both intervals and that's why he's using the terms interchangeably in a sentence?