This is probably a good tool for a few aspects of getting someone started on the guitar, but honestly I think it's the minority. Hitting the right string while

This is probably a good tool for a few aspects of getting someone started on the guitar, but honestly I think it's the minority. Hitting the right string while holding down the right fret isn't that hard. The problem is doing it in such a way that you can raise your speed or start hitting multiple strings at once with different fingers. And doing that isn't that hard, but it requires good instruction and a daily investment of a small amount of careful practice by the student (about 10 minutes to start, 20 or 30 minutes a day later -- once the technique clean, then you can begin the long ramp up to being the kind of monster that can play 8 hours a day). I taught someone the equivalent for violin in 6 months (and the initial learning curve on violin is absurdly long compared to guitar). That wasn't the limiting factor, though. The limiting factor was the music: timing, ear training, articulation, dynamics, how to shape a melody, how to read music, how to write music, a body of carefully studied examples to be able to work on...