OVM Plugin has released a free mono synthesizer instrument with integrated sequencer.
Diatonica features 2 oscillators and a sub oscillator, a multimode filter, advanced sequencer, as well as onboard chorus, delay and reverb effects.
A lot of parameters may be randomized, allowing lots of different modulations.
The sequencer section offers lots of possibilities to take your sequences to another level once programmed. You may also record pitch directly from your keyboard.
Diatonica is available to download in VST/VST3 plugin formats for Windows (64bit).
More information: OVM Plugin