Going to tag along on this thread too.

I am another "belt" it out singer living sandwiched between flats. Upstairs taxi driver with odd hours and downstairs, twin toddler boys that I fear waking up as their parents need every moment of rest they can get.   

I also suffer from melodic drift on a continental scale. Great advice here. I am learning Appalachain dulcimer and hopefully using this very simple instrument will help to keep my voice on track. I do, listen listen and listen again to really learn melody. But my brain is very creative and likes to embellish, improvise to my ruin. Alas!

What Rosie said about lazy brain wanting to resolve sequences the easiest way, makes perfect sense. Like water taking the easiest route to flow down. Now how do I build mental locks and weirs to make the song go where it is meant to go?