[El Tenore]

Out of curiousity, why is a piano keyboard needed for reviewing? To play and hear them without instrument?

For a choir conductor the piano is a must, and its not allways possible to bring a real piano. On outdoor conserts, bar giggs and so on.
Im going to replace my pad and could choose cheaper things than Ipad pro (12,9"). The Forscore app has a piano, but runs only on Ios.
With Mobilesheet i would get away with a third of the price.