Artists routinely let their hair down — metaphorically, anyway — but the Danish String Quartet’s concert appearance in October gave a new, specific meaning to the term. Midway through the concert opener, Bartok’s Quartet No. 1, violist Asbjørn Nørgaard’s face suddenly disappeared behind a curtain of dark blond hair. Clearly unfazed, Nørgaard kept up with his colleagues, delivering a terrific performance. When the quartet emerged after intermission, Nørgaard’s ponytail was securely in place and the quartet’s performance of Beethoven’s String Quartet No. 14 in C# minor, Opus 131, was breathtaking. These guys are so in sync with each other that a bad-hair moment doesn’t get in their way. Chamber Music Cincinnati, cincychamber.org.