The Renaissance Singers arrived for their Sunday afternoon performance to discover their trailer was missing.
The Singers' president Guy Broadley said the trailer was locked and in the carpark at the back of St Peter's Church.
"In this day of portable grinders, padlocks and other such defences are no deterrent to determined criminals."
Broadley said the theft was reported to the police but they were advised to go online or use the 105 number.
The choir members were then involved in setting up the few remaining riser platforms that had been stored in the church overnight, and two of the four sets of lights, before their 1pm rehearsal.