IsoPad is described as 'is the free Windows touch MIDI keyboard. It contains three different keyboard layouts. One of them is the familiar piano fingerboard. However, the others are way more suitable for modern touch interfaces' and is an app in the Audio & Music category. There are eight alternatives to IsoPad for a variety of platforms, including Windows, iPhone, iPad, Android Tablet and Android. The best alternative is Perfect Piano, which is free. Other great apps like IsoPad are Free Piano (Free, Open Source), EveryonePiano (Free), MidiKeys (Free) and Perfect Piano Player 3D (Free).
Perfect Piano is a smartphone app designed to teach players how to play and record piano songs of their own using their smartphone. There are many plugins to allow you to change the sound of the piano to things like a guitar, harp, and cello.
MidiKeys is a small application for Mac OS X that presents a miniature MIDI keyboard onscreen. You can use the computer keyboard to play MIDI notes, or click on the keys with the mouse. There is also an option to select a MIDI source and see incoming notes played on the keyboard.
TouchDAW is a full-featured DAW control and general purpose MIDI control app for Android™ tablets and phones. It allows you to remote control popular digital audio workstation software as known from standard hardware control surfaces.