<p>:) Your welcome!
And of course they could distinguish between voice and strings, but they say it MUST be a solo piece, so I wouldn’t go against their requirements. Maybe you could call them. The song Neon shows a lot of skill but I see your hesitation to do it without singing: they might find it a tad repetitive with only guitar.
Manhattan would be a GREAT idea though! You can really show off clean technique and soul, just like Europa. :)</p>