LH Rubbing is a polyphony synthesizer app for iPad running on iOS 9.3 or later.
It sounds very analog.

There are three wave oscillators, one noise oscillator, two LFOs and one three type embedded filter (low-pass, hi-pass and bandpass).

Each wave oscillator can generate three kinds of waveform which are triangle, square and saw wave.

LFO can be attached to different modul for different modulation or control such as OSC Pitch, PW, Filter Cutoff Frequency, Filter Resonance and OSC Output Mixing.

The frequency and amplitude of the 1st LFO can be modified by the 2nd LFO.

Pitch, Filter Cutoff Frequency and Resonance can be controlled by the ADSR envelope generator.

The Keyboard Rubbing brings up vibrato while control the vibrato rate and depth.