Thieves stole a trombone worth thousands of pounds from the boot of a car.
It was taken from a black Volkswagen Golf in Ritcroft Street, Hemel Hempstead between 12pm on Thursday, April 16 and 5.30pm on Friday, April 17.
It is a Rath R4-F trombone in a Marcus Bonna Tenor case and has serial number 213B.
The thieves also stole a bag from the boot too but police say it is unclear how they got into the car.
Anyone with any information about what happened or where the musical instrument may be now is asked to call the Herts Police non-emergency number 101, quoting crime reference number D1/15/2369.