I'm not really sure about the type of technology you mean, and having ever write precisely zero decent songs, am not perhaps the best to comment (mind you I've written better stuff than some who claim to be 'songwriters')

I tend towards Paul McCartney's view: "If I can't remember it, then no one else will"

I don't fully understand what you mean, but surely a dictaphone with 'the melody does this' 'the bass does this, etc would suffice?

Or maybe I'm missing your point?

Not sure why high quality is important for a sketch