The U1J was designed based on Yamaha's acclaimed U series upright acoustic piano line. This is the 'Silent' version.
The Yamaha U1SH2 silent piano is a traditional acoustic upright piano with the added bonus of a high quality silent system. This means you can play and practice 24-7 with headphones on and not bother anyone. It also takes Yamaha’s free app Music Pianist that have loads of great features that work with the piano.