Flowkey - The easiest way to learn piano with your iPhone or iPad
Adobe Acrobat DC - Make your job easier with Adobe Acrobat DC, the trusted PDF creator. Use Acrobat to convert, edit and sign PDF files at your desk or on the go.
Yousician - Learn to play music at home, at your own pace
Sumatra PDF - Sumatra PDF is a slim PDF/DjVu/EPUB/XPS/CHM/CBR/CBZ/MOBI viewer for Windows.
Melodics - Melodics is a desktop app that teaches you to play MIDI keyboards, pad controllers, and drums.
Wondershare PDFelement - All-in-one PDF editor