No sound
There's one octave of keys on the piano that I can't get seem to hear any sound come from the instruments when I touch the keys..
No way
You see one octave. It is a mystery why Apple would have this in their store.

A simple virtual instrument app designed for children, featuring piano, guitar, and drum sounds. It includes automatic performance modes using accelerometer controls and the ability to record and play back songs.
2.1
May 8, 2017
This app has been updated by Apple to display the Apple Watch app icon. corresponding to iOS10.
MoreDokodemo Gakki allows you to play piano, guitar, and drum sounds. You can switch between these instrument tones using the screen buttons.
The automatic performance uses the device's accelerometer. By tapping the table or moving the terminal, the instrument will play automatically. Songs used in this mode can be recorded.
Yes, you can record songs using the 'Rec' function. This recorded data can be used in the 'Play' mode. Please note that only one recording can be stored at a time, and new recordings overwrite previous ones.
Dokodemo Gakki is specifically designed as a toy for children. While it has an age rating of 4+, its precision is not intended for serious musical play. It's meant for simple, fun exploration.
Dokodemo Gakki is available for iPhone, iPad, and iPod devices. It was released on October 15, 2011, and its latest version is 2.1, updated on May 8, 2017.
No, Dokodemo Gakki does not contain advertisements. It is a free application without any ads to interrupt the user experience.
User feedback for Dokodemo Gakki is limited, with a current rating of 1.0 stars from 2 ratings. This suggests a very small user base or potential for improvement based on early impressions.
Dokodemo Gakki was last updated on May 8, 2017, to version 2.1. This indicates that the app has not received recent updates.