I highly recommend watching gameplay of this in the PS4 layout, specifically Extreme. I think you'll see why the A's are only in the beginning and the instrumental parts.
If the icon is uses to match the singers, why dont they use same thing for 'Hikyou Sentai Urotander' which include blue X for kaito, green triangle for miku and red circle for meiko?
Don't worry. You just have to clear a song once, and they'll unlock for that respective song. I did it all on hard difficulty, so I'm not sure if any difficulty will do.
