Can I do my piano Grade 6 during year 13 and make it count towards my UCAS points?

I have known piano for a long time but never wanted to take a grade in it. However, I have noticed that piano grades can make positive contributions to your UCAS application, and even though it may not make much of a difference (especially since I want to apply for engineering), I don't see why I shouldn't get at least a grade 6. I am wondering, can I do the piano grade during next year and still make it contribute UCAS points, or do I have to do it by the time I make my application?

Before you pursue this approach, please ensure your target universities will accept UCAS points from music grades.

It's not uncommon to see phrases like:

"The entry requirements for this programme are 100 UCAS tariff points from level 3 academic qualifications."
-or-
"104 UCAS points from A-Levels (we also accept UCAS points from alternative Level 3 qualifications including: BTEC Nationals, the International Baccalaureate and Scottish and Irish Highers)."

As you imply in your question, you musically ability is unlikely to be relevant to an engineering degree.

I understand it may not be relevant, but would it make my application any less attractive if I do put down a music grade? And anyways, as was my main question, would I still be able to do the music grade in year 13 after my applications or do I have to do it before?