One of my favorite musicians to play with is blind. He's the guy playing mandolin on my Soundcloud link in my signature. He's also a really good guitarist.

I started playing with him before he lost his sight completely. Even though his sight got worse by the day, his playing just kept getting better.

He introduced me to playing Dawg music and I introduced him to some classic Jazz tunes. We both already played bluegrass and fiddle tunes.

I haven't seen him in a few years but I do know he's still playing, even though he's been totally blind for the last 15 or 20 years.

In short, ... you can play without fret markers if you have to. I've never had to so I still use them.

Bob
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http://soundcloud.com/bobcflatpicke/music-in-the-mountains