I'm sorry to say but the 'Variation beats Depth' myth is a lie.
Cambridge, for one, have an overwhelming preference for depth. Most other top uni's are the same, they only really care about A-levels related to your chosen field.
However, you do have Maths and Further Maths which are obviously as related as can be and Economics which goes well with maths at A-level.
If you really wanted to maximise your A-level potential then I'd say replace Music with a science.
Also, economics is not a requirement or even favourable for a economics degree. If you REALLY want to maximise your CV in terms of A-levels for uni, take another science.
A top, top A-level selection is Math, Further Maths, Physics and Chemistry for example.
Your subjects at the moment though are good anyway so I personally wouldn't worry too much unless you are looking at a top, top course.