This is an Android application that plays a sound of the selected note (every note from C4 to H4), with the extra ability to choose the pitch of A4, from 392 to 489Hz, in relation to which all notes transpose accordingly. The range of frequencies corresponds to the range of historically recorded A4 pitch frequencies, as the ultimate goal of the app is to be an all-in-one tuning tool for all instrumentalists and singers of music of any era.
You can install it using the latest apk file from Releases.
For the equivalent desktop application see DiapasonFX.