I think you can make a focus on any one of your senses a mindfulness exercise. If you pay attention in the moment to the sensual experience that you are having. You could use your breath alongside the music in order to anchor yourself in the present moment. Or use the music and the experience of the sound in your ears and perception as the anchor itself.
I think this would actually be harder for a beginner in mindfulness than a simple focus on breath because music is highly complex and could easily lead you away from the present moment into fantasy or a chill out experience that would have a great deal of value for many of us here, but that you couldn't actually call mindfulness meditation.
My view is that every part of life is experienced through the senses, so by paying attention to external and internal stimuli in the moment you can potentially go through your entire day as a kind of mindfulness meditation. Sometimes I find myself being able to do this at certain points in my day. But it is a kind of attention that is best learnt first in a simple way, otherwise it is not so easy to do, in my experience at least.
I find that formal periods of mindfulness using a simple focus on breath are the best way to learn this kind of attention, which you then become more and more adept at applying in other moments of the day.
Having said that, when I first tried to sit to meditate, I also used music because my own thoughts and emotions were far too disturbing to allow me to feel safe with myself. The music gave a focus other than myself so that I could be calm enough to pay attention to my breath. Once I learned that I could do this I stopped using the music because for me it was a distraction, actually a sort of avoidance of the difficult emotional experience. I think the goal of mindfulness meditation is not to chill out, but to pay attention to whatever your experience is without judging it. So sometimes my meditation doesn't feel nice or relaxing, sometimes it does, but it is what it is and that is the point. When those difficult emotions arise I try to observe without pushing them away or hanging onto them and in this way I can also let them go because with the next breath comes the next moment and something new to observe. Somehow working at the non avoidance, the non judging, the acceptance, the letting go .. all that good mindful stuff, somehow it gives me the inner strength to find peace and patience at other points in my day. Not necessarily in the meditation itself, that is more a sort of training time, and it can be tough. Now I don't think I could do this kind of work on myself with music playing. But it helped me to sit still to begin with.
In other words, mindfulness does bring calm into your life by giving you skills to accept yourself and your experience without being swept away in the storm of everything, but that calmness doesn't magically appear in every mindfulness meditation you try and if you are expecting it to be an instant result like that they it will be disappointing and frustrating to try. Most of the guides I have read suggest doing it everyday for 40 days, or eight weeks, or similar, before you really start to experience how it can be good for you to have the skill of paying attention like this.
Do we need another thread for meditation types that aren't strictly mindfulness that help in other ways? I have a friend who listens to those vibrations and things like that. There do seem to be endless ways to meditate that aren't mindfulness. Where you do get instant benefits like relaxing or sleep or whatever. I personally am focused on mindfulness, whether any particular meditation session relaxes me or not, because that is the particular tool that is helping me. So I started this thread to share tips. But it is not the only thing that might help people using this website. I don't think I am the one to start another thread because it is not where I am at right now. But if someone else reads this and thinks it would be a good idea then maybe they would start it?
By the way ATTMP I am not implying that what you are doing is not mindfulness, just that it got me thinking and all this burbled out.. for me it would be hard to use music and remain mindful, but that is just personal experience.
There are a lot of ideas out there at the moment that use mindfulness as a term because it is kind of a popular word so I feel like I want to use this thread to clarify for anyone reading who is new to the idea. Especially because I see a lot of meditation videos on YouTube using this or that music or sound or vibration or whatever and a lot of it is actually to achieve a particular state of relaxation or whatever and not actually about staying in the moment as you find it. And, I guess I think it is important that people understand the distinction between the different sorts of meditation. Because if someone is planning to use a tool like meditation in a specific way to improve their mental health then it is good to know which tool does which job.