Judging by this Gold Les Paul, the answer is 14: including Taj Mahal, New Wave icon Elvis Costello, Reed Mathis and other musical luminaries.
The hallowed axe is being sold by good cause impresarios Charitybuzz in benefit of the Pinetop Perkins Foundation.
Founded in honour of Pinetop Perkins, one of the last great Mississippi bluesmen active in the 1920s who died in 2011, aged 97, the foundation aims to provide encouragement and support for young people at the beginning of their musical careers.
Also benefitting from the sale is The Blues Foundation which, affiliated with more than 175 worldwide blues organisations, is aiming to keep the genre alive.
And the guitar's donator is himself no stranger to the blues: guitarist Hubert Sumlin (b. 1931) whose career includes time in Howlin' Wolf's band and being voted number 65 in the Rolling Stone 100 Greatest Guitarists of All Time chart.
Sumlin continues to tour today, and is cited as an influence on later rock legends including Eric Clapton, Keith Richards, Jimmy Page and Jimi Hendrix.
Aside from Taj Mahal, Costello and Mathis, other famous autographs on the guitar include Wavy Gravy, Mickey Hart, Bill Kreutzmann, Keller Williams, John Butler, Levon Helm, Susan Tedeschi Trucks, Derek Trucks, Oteil Burbridge, and Hubert Sumlin.
Also worthy of note is the guitar itself. Celebrity signed guitars are often budget-produced imitations of Fender Stratocasters and other eminent axes, worth little without their celebrity-added ink.
But Sumlin's guitar appears to be a real Gibson Les Paul Gold, which certainly won't hurt its auction value when it is sold by Charitybuzz. Although the lot notes don't specify if the guitar has been played by Sumlin himself.
Bidding closes tomorrow (August 10) at 2.30 EDT. Watch this space for all the latest charity auction news.
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