( link here: synprezfm overview )
and thought that it would be nice to upload the original manual for Yamaha DX7...
So here you go:

dx7e1.pdf |
Common Fm-
It is smaller in scope but if you don't know how to program Fm synthesizers
( I don't ) this one allows you to just fool around and get something out of it without losing control-
Think that this can be a synthesizer to be used to intuitively learn about
programming Fm without going into ( no please no... ) mathematics and logical thinking.
While Synprezfm is a big meal with a soundbank of over a 1000 sound and can load sysex patches from the original Yamaha DX7, and have the full programability of a DX7.
Common Fm is more relaxing,
like a nice Sunday brunch.
Both being excellent and like been said before being for free...
What is stopping you from trying them out?
Playstore links:
SynprezFm
Common Fm
Sailing on
Frank Malm