Embedded is a song that helps one of my students a whole lot with her concentration (those so-called ADHD symptoms simply disappear). I got it from the other music thread on here.Why I think the songs I have now work so well is the harmony - and since they're not in English/German, which she understands, there's no distraction.
I could really use more choir music to compile a playlist, so please share your favourites! Bonus points for vocal-only, bonus points for non-English.