Officers have now issued the pictures of two men they want to speak to about the theft.
The victim noticed his two clarinets – worth in the region of £5,000 – had been taken when a train from Milton Keynes and Manchester pulled into the station on Sunday 22 March at around 10.50am.
Inspector Mike Wedderburn said: “The victim stored his clarinets in their case in the overhead luggage racks.
“When he got up to leave the train, he discovered the case had been taken.”
“The owner is obviously very keen to get them back.
“I think the two men in the picture can help us with our enquiries into this theft. Please tell us who they are.”
Anyone with information is asked to contact British Transport Police on 0800 40 50 40, or text 61016, quoting reference PSUB/B14 of 07/04/2015.
Information can also be passed anonymously to the independent charity Crimestoppers on 0800 555 111.
