The incident occurred about 1:45 p.m. at the Jackson Red Line station. Chicago police said a woman in her 30s approached him and began yelling at him with him before grabbing some sort of knife or sharp object and stabbed him several times in the arm.
It was not immediately clear what prompted the woman to confront the man, police said. An amp and broken guitar were left behind after the attack.
The 26-year-old man was transported to Northwestern Memorial Hospital in serious condition with multiple stab wounds, according to the fire department. He is expected to recover.
The woman was arrested nearby after a witness identified her and taken to a hospital for treatment, police said. No charges have yet been filed.
Several Red Line riders said the musician is well-known to those who commute through the Jackson stop. They said they are hoping for a speedy, full recovery.
Red Line trains were standing at the Jackson station for a period of time as police responded. Trains were running with residual delays later Tuesday afternoon, according to the Chicago Transit Authority.
Chicago police did not immediately provide information about the investigation or if anyone is in custody.
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The Sun-Times Media Wire contributed to this report.