#1
In Troy Stetina's Speed Mechanics book there is a chapter on intervals in which he explains and plays them. Stuff like Per 4, maj 3, unison, Etc.

I don't really understand what to do with these intervals or how they are applied to music, songwriting, theory, or whatever. He says to memorize the shapes and sounds, but never fully explains the use of them. What am I supposed to use the intervals for and how do I apply them to learning, playing and writing music?
#2
IF you can fully recognise intervals, you should be able to work out anything. That includes melodies made up in your mind.
Quote by IROBOTInferno
Dumbass that is a classical guitar, use nylon strings or the neck will crack... and not the kind you were smoking when you wrote this.