Heavenly shades of night are falling, it's amok time...
Spock feels an urgent need to beat something.
This Star Trek moment occurs during episode #34. This episode was first broadcast on September 15, 1967 and later repeated on April 26, 1968. It was the first episode of the second season, and the first to air after the series moved to Friday nights at 8:30pm. In "Amok Time," Mr. Spock returns to his homeworld for a brutal Vulcan marriage ritual which results in the "death" of Captain Kirk.
Like adolescent boys around the world, Spock attempts to forget his frustration by playing a musical instrument.
During that scene where Spock plays the Vulcan lyre, this is the strangely haunting, yet beautiful music (Sol Kaplan and Gerald Fried composed) used, called "Mr Spock." I always imagined Spock was playing the guitar part on the lyre.
Here is the music played during the ritual. It's appropriately titled "The Ritual-Ancient Battle-2nd Kroykah" (I shortened it by about a half). You may remember Jim Carey's interpretation of it in The Cable Guy.
Dr. McCoy (hoping to prevent Kirk's slaughter) injects the Captain with a neuroparalyzer drug that simulates his death, and ends the ritual.
Back on the Enterprise, Spock lowers his guard momentarily when he realizes Kirk isn't dead.