MILFORD, PA — Four-hand piano team Dongsok Shin and Gwendolyn Toth, aka Duo Appassionata, will perform Saturday, June 14 at 5:30 p.m. in the Great Hall at Grey Towers National Historic Site, and Friday, June 20 at 8 p.m. at the Hawley Silk Mill. They will be playing a reproduction of Wolfgang Amadeus Mozart’s fortepiano, which was made in the 1770s or 1780s.

The program will include a couple of Mozart’s pieces, but it will also feature sonatas by two of his contemporaries: Muzio Clemente and Johann Christian Bach, the youngest of Bach’s 20 (yes, 20) children. J.C. Bach and Mozart were friends, and they performed four-hand piano together when little Wolfie was touring as an eight-year-old sensation.

Fortepianos were the new thing when Mozart was growing up in the 1770s. Unlike the harpsichords they replaced, fortepianos allowed performers to vary how loud each note would sound.

Unlike today’s grand pianos, though, fortepianos produced a more mellow sound, and they only spanned four or five octaves.

Tickets cost $20 at the box office or $15 when purchased in advance at kindredspiritsarts.org/. The public can also buy tickets at Books and Prints at Pear Alley, 220 Broad St., Milford. Children under 15 are admitted free. These events are presented by Kindred Spirits Arts Programs, a nonprofit 501(c)3 organization of volunteers.