Yes, as a licensing lawyer, I have more than a clue as to what you can do.
You have a bar, so you already have a Premises Licence which details all of your licensable activities, inlcuding the sale of alcohol and anything else which needs licensing, inlcuding the playing of music or the facilities for people to do so.
If you had a Public Entertainment Licence prior to 6th August, you could have applied to transfer these rights to your new Premises Licence under the new Licensing Act. If you did not do so, you may be acting unlawfully by playing music. I cannot advise further unless I know what you had then and have now. There is the possibility that music is "incidental" and not licensable but that depends on its extent and frequency and whether people are attracted by it.
The other aspect is Performing Rights as said before