The "sixth hindrance" - Earworms!

[Mkoll]

Yes, what culaavuso just said. I'm not saying you have to avoid all music as this would be impossible in a modern environment and this attitude would tend toward aversion. I'm saying what you could try is avoiding questing for music for your own enjoyment. The desire to seek out music to listen to feeds the desire to create one's own music in one's own head. If it's not being fed, it will eventually stop on its own accord. Until it's fed again.

Of course it's perfectly acceptable to be a householder and listen to music so it's not like this is an injunction. And it sounds like your practice is doing just fine.

[Spiny Norman]

We tend to think that concentration is about forcing out anything that isn't concentration, rather it's about maintaining a mind that is stable and centred around the object despite whatever thoughts are arising and passing away. The music doesn't have to have the ability to take you away from the object unless you let it, doesn't have to be a cause for aversion unless you let it.

[atipattoh]

And this is a good observation too!

….. this probably indicates that you are pretty worry/complication free these days which is a good thing.

…… There is often lots of piti and some sukha arising. ....
………….. my practice is Jhana – oriented…….

I think we all have our ‘6th hindrance’, the only different is the ‘appearance’ and intensity. Especially when strive for some thing and it seems does not achieving the goal and yet we continue to sit, the will just loose its momentum. Then the mind would do what it normally does.
Once at the retreat, I literally build a machine with movement simulation, possible fault analysis with immediate remedy until I satisfied with the design; this was my job though it was almost a decade ago; when I let the mind to continue at the point that I almost give up; towards the end of the retreat. In actual fact, I wasn’t meditating, rather thinking.

I guess the piti and sukha that you experience is likely metta bhavana. So why not you try to embrace the experience with metta bhavana, a little compassion towards that sound experience; telling yourself and making resolution:” It’s good to be relax and experience smooth sound; but , I’m not going to progress well in my practice if I continue hearing it. In this sitting may I know just my primary object-the Breath!”
Something like that; determination is a very good quality, use it.
Do this at the beginning of sitting, then sitting relax for awhile before starts applying thoughts on breath.
On another retreat, I did something similar on sound issue but mine was lower intensity than yours. I heard it even when I was not sitting but it was not cause by habitual in nature so I would consider less intense than yours; a single resolution alone resolved the issue. Yours may need a little more work.

Edit:Or could it be a combination of a little bit of this, a little bit of that and a little bit of those; a new ‘dish’ on the menu.
Investigation into combination of sensual desire, sloth and torpor, and restlessness; perhaps? The elements of each of these hindrances could be too fine to classify the whole issue into one specific hindrance.

[Goofaholix]

Yes. It doesn't take me off the breath or prevent the arising of some of the other factors that are useful in meditation. It's just a bit like that guy that invites himself to your house but for some reason doesn't realize it's time to go. You'd kind of like to turn in for the night. You say "Ok, well I'm going to turn in for the night." He says "ok then" and doesn't get up. He's still your friend. You can't really kick him out but you kind of wish he'd go. :)

A good observation, in other words it is not self.

[Lostegasa]

It's like my ego's last guardsman going "haha! You will never get into this jhana!"

Don't care about an ego against your achievements, this is not true, ego is like a machine, you won't speak to it as a living being.