The synthesizer module, designed by Donald Buchla (Tom Oberheim did not participate in the development) to recreate the sound of two legendary families of synthesizers - Moog and Oberheim. The name is the abbreviation of Oberheim-Moog.

Ob-Mx is based on the principles of many Oberheim synthesizers - a motherboard (containing a control unit, a mixer and an output module) and voice cards. In the basic configuration, the module is duophonic (it contains only two voice cards), but it can be expanded to a twelve-voice one by adding voice cards.

Each voice card contains two voices, each of which is built on the basis of two voltage controlled oscillators (VCO). For the construction of VCO specialized CEM3374 chips were used which allow to obtain oscillators with high stability. For each voltage controlled oscillator, a sawtooth, triangular or rectangular waveform with a fine-tuning adjustment can be selected. Hard sync modes and ring modulation are available. A white noise source is included in each voice card.

The most interesting in OB-Mx is the filter section, which allows you to achieve the specs of both Oberheim and Moog filters:
VCF MM (Minimoog) - a four-stage low-pass filter (LP) with frequency and resonance adjustment. Has a slope of 24 dB per octave.
VCF OB (Oberheim SEM) is a multimode voltage controlled filter (LP, HP, BP) with adjustable cutoff frequency and resonance. It has a two-step structure with a slope of 12 dB per octave.

To provide modulation capabilities the synthesizer includes four independent ADSR envelope generators and three low-frequency oscillators (LFO).

LFO can produce a saw, a reverse saw, a triangle and a sample&hold (S & H).

OB-Mx has limited MIDI support: changing the position of the parameter control knob is not transmitted via MIDI, and it is also impossible to change, for example, the filter cutoff frequency except manually.

Famous user list includes Apollo 440, Nine Inch Nails, Sneaker Pimps, DJ Spinna, U2.