In a 2007 interview [2] he says that, based on Josh Waitzkin's appraisal, his (unofficial) ELO rating would be around ~1400 ELO
[1] https://www.nytimes.com/2008/06/07/arts/music/07clan.html [2] http://www.uschess.org/content/view/7924/349/
Edit: Updated with source
In a 2007 interview [2] he says that, based on Josh Waitzkin's appraisal, his (unofficial) ELO rating would be around ~1400 ELO
[1] https://www.nytimes.com/2008/06/07/arts/music/07clan.html [2] http://www.uschess.org/content/view/7924/349/
Edit: Updated with source