This could have to do with restrictions on country as some developers prefer to limit Beta testing so if you can not download it maybe wait until it released officially?
Play Store info:
Monophonic synthesizer application that delivers a wide variety of sounds, MIDI support, and a high quality synthesis engine.2 Alias-Free(Low noise), Stereo, Dynamic Waveform Generators (multiple synthesis techniques)
10 32-bit Wavetables
Custom designed, unique, waveforms.
FM & RM Synthesis via the modulation matrix.
Standard VA-Style Waveforms Saw, Pulse/Square(with PWM), Triangle, Sine
1 Low Pass Filter with 3 different modes.
Completely stereo signal path.
Tape-delay inspired stereo delay (can function as a flanger or chorus effect!)
Flexible Modulation Matrix
2 LFOs (Low Frequency Oscillators) 6 different waveforms with 2 built-in destination routes each. Tempo sync + retrigger along with an error control to add chaos.
4 Envelope Generators ~ ADSR
High quality sound engine. 32-bit floating point internal processing. Adjusts to individual device's optimal settings.
4 Slot Modulation Matrix
Basic MIDI support - Plug-and-play with an OTG cable. Supports pitch bend, mod wheel, velocity, after touch.
Improved latency that takes advantage of the latest Android improvements. Optimized for Kit Kat 4.4.2. See release note 1 below.
Page Based User Interface - Swipe left or right to navigate through the different parts of the synthesizer.
Keyboard designed to be easy to play and to be appropriately sized for most people's fingers.
Minimum System Requirements:
Android Version 4.4.2 "Kit-Kat" or later.
1 Ghz processor or better (multi-core recommended)
1 GB RAM
External speakers or headphones are recommended.
Demo Version Limitations:
Presets cannot be saved.
Latency is ultimately dependent upon your hardware and version of Android. The demo version is provided so you can try it out on your particular device.
Android MIDI device support only works for MIDI controllers that require no additional or proprietary drivers. i.e. Generic MIDI Devices. Consult the Android documentation for more information.