This app is really complicated, but once you learn about it, it is a really really good overlaping music compilation maker.

This website has key techniques to help with sight reading and interpreting the piece in your mind faster. This website also helps understanding sight-reading on different levels, not just note by note.

This website helps recognize different scales by ear, without looking at what key it's in. This also helps greatly with hearing different trichords, harmonics, and melodic scales.