Sentence:  So Apollo's instrument, a sixteenth-century lira da braccio with nine strings like the Greek <WSD>enneachord</WSD> given over to the nine muses, serves as the culmination of the lyre's development, as pictured in the Parnassus by Raphael. 
Meaning of the word marked with <WSD> tags:  An ancient Greek nine-stringed musical instrument.