XotoPad is described as 'Play MIDI instruments on your Windows tablet and control your studio gear. XotoPad turns your multi-touch device into a full-featured MIDI controller with chords, scales, faders, and more' and is an app in the Audio & Music category. There are four alternatives to XotoPad for iPad, iPhone, Windows, Android and Android Tablet. The best alternative is Navichord, which is free. Other great apps like XotoPad are IsoPad (Free), Midi Studio (Paid) and TouchDAW (Paid).
IsoPad 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.
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.