Try to understand the workflow of how your users are using your application now and also know the goals of how you want them to use your application. The tracking of where a user goes when using an application is called user flow. Once you understand what you need, then you can think about how to do so. The what must come first in order for the how to be any good.
Talk to people (not just your users) about their experience with music players. Which ones they use, what they like about it, what they dislike about it, what they wish it had but doesn't have, and more questions similar to that. This is called a user interview and here's a great video on how to conduct one.
Then you ask this person who is new to your application to use it with you watching. Don't tell them anything about it before hand and watch what they do. You may want to record this so you can look back on it later. Notice where they hesitate, where they mess up, and where everything runs smoothly for them. Afterwards, ask them about their experience including if they were looking for something they couldn't find, where they expected to find it, if each button did what they thought it would, etc.
Do this over and over again. You'll quickly find what users are needing in, what parts of your application are confusing, common actions that they do, and what often times get good feedback on the sorts of things you should be working towards. That does not mean that you implement everything (or even most things) that users request. That means you use the information you've gathered to develop what they need and put that in your application.
Additionally, users have patterns that they are used to. Look at how other players do things and consider building your application similarly. This prevents the users from being required to learn a whole new scheme and they can user your application quickly after starting to use it. Also read about the way users look at pages and how to visually lead people to items on your page.
Besides that, the open source community is generally pretty nice. Post a message saying what you're needing and see if anyone gets back to you. As for particular elements of the design, if you follow our guidelines for critiques you can ask specific questions about aspects of your design. We'll help where we can if you ask a good, on topic question, UX.StackExchange also answers questions regarding this sort of thing.
