A4 semi-modular synth
A synthesizer manufacturer based in Italy. GRP's products include two analog, semi-modular synths, the A2 and A4. Both are packaged as tabletop units. The A4's architecture contains three VCOs, two VCFs (one a four-pole transistor ladder, the other a two-pole state variable filter), white and pink noise, a ring modulator, two multi-segment envelope generators, two LFOs, a sample and hold, an analog sequencer, and a MIDI interface.
The company's second main product is the R24 analog sequencer, a three-row by 24-step sequencer with multiple skip/loop/stop options and outputs. The R24 comes in a tabletop case, but is designed such that it is compatible with the Dotcom format and can be mounted in a modular synthesizer that uses this format.
Two-pole multimode VCF, with built-in distortion
Additionally, GRP manufactures a line of Eurorack modular synth modules. As of the end of 2018, the lineup includes mostly essentials derived from the A4 and A2, including a VCO, two VCFs, an LFO, a sample and hold, and a flashy output module with ballistic meters.
GRP Web site (English)