Sentence:  Certainly not in Orchestra hall where he has played countless recitals , and where Thursday night he celebrated his 20th season with the Chicago Symphony orchestra , playing the Brahms Concerto with his own slashing , demon-ridden cadenza melting into the high , pale , pure and lovely song with which a violinist <WSD>unlocks</WSD> the heart of the music , or forever finds it closed . 
Meaning of the word marked with <WSD> tags:  become unlocked