This app makes the meantone temperament version of the Christian Zell 1737 harpsichord sampleset available for playing with a MIDI keyboard connected to your iPad or iPhone. To learn about the instrument and the sampleset, please visit http://samplesets.esmuc.info/ .
There is also an equal temperament version and a bundle of both apps. If you purchases one of the apps, you can download the other one for free by bundle completion.
For more information about the app and the underlying Napo framework, please visit the support page http://polaron.de/Zell/ , the Napo documentation at http://polaron.de/Napo and in particular the user manual at http://polaron.de/Napo/manual .