I have finally gotten serious about learning to play a fretless with the purchase of a GW-1. It's lined so that's good. I have a great ear, so that's good. Now, I know that you have to be on the line to be in tune. Then, a little rocking of the finger (vibrato) will cover if you are slightly off. So if you have to be that precise, do you have to commit the song to memory so that you can stare at the fretboard? Or if the answer is, you just practice yourself silly until you just go to the right spot, what good then are the lines? I tried playing a tune without looking and by sliding to reference pitch and working from there and did credibly. Just need some basic coaching.