Congratulations to Kathryn and commiserations to those who missed out this time. Thanks to all the punters who entered from around the world. Unfortunately not many got the correct answer. The odd man out interloper tile of Salisbury Cathedral organ pipes was in fact C3! (See the original picture below)
Spot the odd man out - Solution!
Below is a photo of the beautiful John Loosemore 1665 pipe organ in Exeter Cathedral. Or was. Unfortunately one of the kitties (the culprit has not confessed) chewed a piece to shreds and I had to substitute a shot from Salisbury Cathedral to make up the 16 random pieces for my puzzle. Can you tell which one of the tiles is not from the Exeter organ, but from the Salisbury organ? (You don't have to be an organist or even musical to answer this!!)