All this software use seems like a lot of work to deal with something that should be self-evident if one, you know what note you are singing, two you know what key you are in and three you have a scale chart to tell you the notes.

Having any sort of keyboard that you can play notes together will let your ear know if you are doing something that sounds good together.

As an experiment, I just played a C scale on a keyboard and checked to see what notes sounded good together. Harmony is not hard to understand. You do not need to be a piano player to do these sorts of experiments. You do not need to know that it is the "third" or the "fifth" you are using but it is pretty self-evident if you can count to seven...lol

Understanding basic musical concepts are not difficult. You don't have to call it "music theory". It is not critical if you don't know what a minor third is. Having said that it is useful to know and understand at least basic music theory. That understanding makes using software like BIAB more valuable.

Melodyne can be used to create harmony but it never sounds as good as singing it yourself. Learning to use Melodyne is not simple. Auto-Tune will create harmony and is less trouble to use but cost more.

Billy

“Amazing! I’ll be working with Jaco Pastorius, Charlie Parker, Art Tatum, and Buddy Rich, and you’re telling me it’s not that great of a gig?
“Well…” Saint Peter, hesitated, “God’s got this girlfriend who thinks she can sing…”