FM Synthesizer [SynprezFM II]

SynprezFM 2 is a programmable polyphonic synth with a multitouch dynamic keyboard, arpeggio, effects and 1024 built-in instrument patches. It uses Frequency Modulation, a lightweight method for generating complex harmonic waveforms by mixing or combining sine samples controlled by envelops and LFO. It is able to produce analog style pads, to emulate classic or modern instruments, or to invent new and awesome crystalline sounds.
SynprezFM 2 is also a Yamaha DX7 emulator, that can render with accuracy the sysex files you upload into an external storage directory setup by menu, in order to heighten the experience. You can also create and save your own patches, either by editing one of the (deliberately) unsorted builtin ones, or starting from scratch with the `init voice` function.
It is possible to record WAV, to connect a MIDI keyboard (using a USB/OTG cable for Android Honeycomb 3.1+, or Bluetooth Low Energy for Android Jelly Bean 4.3+), and to take advantage of a small step sequencer. Even small devices can now leverage 2 synthesizers thanks to an optimized layout. To simplify the classic usage, complex functions are now only available in `expert mode` (activatable in the setup page): this regards the patch editor and the new micro-tuning feature.
While you play, you can trigger an after-touch vibrato effect by dragging your fingers on the active keys or shift the keyboard to different octaves. Other performance parameters can be accessed above the keyboard, including 2 types of portamento, a sensitivity range for pitch or volume modulations, and some effects that give a sense of depth when using a headset, especially on plucked sounds. You can also adjust the polyphony to adapt to your device capabilities. Thanks to an optimized core, you can hear up to 16 channels playing together, even on mid-range devices.

[Thank you Caroline, for kindly correcting my english :) ]

BUG FIXES:
- fix countless annoying bugs
- pseudo compressor to enable louder sound
- MIDI support based on Android libraries to address more MIDI controllers
- storage access rewritten to solve first time access problems (and support Android 11+)
- pitch discrepancy on recording (48K vs 44.1K) fixed

EVOLUTIONS:
- wireless Bluetooth MIDI support
- ``MIDI slave`` support
- support for multiple MIDI keyboards
- finer volume and balance scale, wired on MIDI
- ``Scoped Media`` storage mode, mandatory for Android 11
- peak indicator on VU-meters
- drop down menus with pseudo LCD
- output volume operating after the FX processor
- description of the device capabilities in the configuration page
- better MIDI traces to diagnose problems