A 63-year-old man was knocked unconscious when he was mugged for his wallet and his saxophone.
The man was hit in the head in Soar Lane, near Frog Island, Leicester.
His wallet and gold coloured Jupiter saxophone were taken.
Police said it was unclear how many people carried out the attack, which happened at 11pm on Monday, May 16 – the night of Leicester City's Premier League victory parade.
In a statement, Leicestershire Police said: "The city was busy celebrating on the night of this incident and there would have been a lot of people out and about.
"We would like to hear from you if you saw what happened, know who was responsible or perhaps have been offered a saxophone for sale."
Contact Leicestershire Police on 101 quoting incident 16000122161.
