Legal Question in Civil Litigation in Illinois

Re: can I do anything about this

Yes, I would contact the police if you are unable to get ahold of the person who has your belongings. As long as they are yours - and not "the band's" or "his" or "someone else's" possessions, you are entitled to them. The police should be willing to help you obtain the items if this person is unwilling to cooperate with you directly. If he is does not return them, yes, it is akin to theft. However, some police agencies may be unwilling (or unable due to manpower) to do much for you beyond taking a report.

Therefore, if you have taken reasonable steps to try to get the property back legally, and have been unsuccessful, you might want to think about filing suit against him in small claims court - either for the value of the property or for its return. Keep records of all of your communications and requests and anything that he may say or do in response (but DON'T tape conversations without his knowledge - that is illegal in Illinois). Good luck.

Re: can I do anything about this

The police are certainly one option. You can go through local police or try the sheriff's office. But before you show up with police, you really want to try to talk to the person.

Try a couple of written letters that you can keep copies of (make sure to put dates on the letters). You can mail the letters or drop them off at the guy's door. You might also try to meet the person at his job or at a mutual friend's home. If he tells you that he will not return the amp, then you know its time to call the police.