Pianist (also sings a bit) is Rabbi Keilson, the Mashgiach in the Mesivta.
At Ari Goldwag's wedding, he spotted a piano in the hotel hallway outside the ballroom and made himself comfortable there. After a few minutes of his playing, a lady peeked out of an office window overlooking the hallway and commented to the effect that it was the most beautiful thing she had ever heard. This was coming from a person whose job was probably to sit in this office right above the piano and who heard it played regularly.