Final answer:
The Musicians Union threatened Duncan with a strike.
Step-by-step explanation:
The Musicians Union threatened Duncan with a strike.
In labor disputes, a strike is a common tactic used by unions to apply pressure on employers. A strike is when employees refuse to work until their demands are met.
By threatening Duncan with a strike, the Musicians Union was indicating that they were willing to stop performing or providing musical services in order to achieve their goals or negotiate better terms.