This app makes the sample set of the Grenzing organ of the Escola Superior de Msica de Catalunya (Catalonia College of Music) available for playing with MIDI keyboards and a MIDI pedal connected to your iOS or macOS device. To learn about the instrument, please visit http://samplesets.esmuc.info/ . Sound and image files are incorporated into the app with the kind permission of the sample set creator, Pere Casulleras, so you don't need to download and install any additional data.
For more information about the app and the underlying Napo framework, please visit the support page http://polaron.de/Esmuc/ , the Napo documentation at http://polaron.de/Napo and in particular the user manual at http://polaron.de/Napo/manual .
*** For your attention ***
This app is a huge download of about 1.3 GB. Make sure there is enough free SSD space on your device.