The vast majority I have read and viewed about music theory has to do with harmony. In contrast I feel like I haven't seen much at all on melody other than the very general idea of scales which tells you what the prime candidate tones are for your melody. So I'm wondering if I am missing a bunch of stuff, or if theory as it relates to melody is less developed or just less involved than that of harmony. In my own playing, I have definitely gotten the sense that the right-ness or wrong-ness of the next note in a sequence of notes is influenced by rhythm, and my guess is that that has to do with whether certain notes fall on strong or weak beats or signify the end of something (e.g., the song, a section), but I haven't yet seen anything that explicitly addresses that - that allows me to make sense of my ad hoc observations (to say...oh, that's why that sounded good [or bad]). Are there any tutorials on this sort of thing? Is it something that is too wide open and perhaps subjective to be pinned down and taught?