iTabla Pandit Studio Pro provides a simple on screen MIDI piano keyboard, for playing the harmonium:
You can use it like a virtual MIDI piano. You can map any note on the keys. To learn how to define the correspondence of shrutis or notes and the device keys, see 👆 The MIDI mapping.
You can control the main tuning parameters from this page, it is useful if you want to play the harmonium along while playing a song or a youtube video, you can tune your instrument according to the pitch used by the musicians in the video.
👆 Connect and use MIDI devices