After years of looking for a reasonable priced OB-1, one fell into my lap. Actually, I had borrowed my good friend David's OB-1 for a while and he eventually made a deal with me. It now resides at Ka-boom as part of the permanent collection. Thanks David! David's entertaining blog on synths and life can be found here: http://thecompleatsynthesizer.com/
The Oberheim OB-1 was the first monophonic synthesizer to have any sort of memory bank. This means that you could save the knob settings and recall them in order to instantly change the sound, rather than having to memorize or map the position of each knob and turn them all to another setting in order to change the sound. From a studio environment, I prefer the latter because you always get something slightly different, but for a live setting, memory does prove to be important.
Sonically, the OB-1 sounds pretty great. Some call this a glorified Oberheim SEM with a keyboard, but it is not. One of the main reasons for me to say this is because the filter is completely different. On the SEM, the filter is a multimode filter that does not go into self oscillation. On the OB-1, the filter is only Lowpass, 12 or 24 dB/octave, and the resonance will go into oscillation.
The oscillators can sync or cross modulate, but there is only ON/OFF for these options and no variation or amount in between. Another limitation of the OB-1 design is that the oscillators and noise are either ON/HALF/OFF. This makes any kind of intricate mixing between the sound sources next to impossible. One unique feature is that each oscillator has a sub oscillator that can be switched in as well.
At first glance, it looks like a PWM (Pulse Waveform Modulation), but it can also change the Triangle Wave to a Saw Wave, depending on which waveform is selected. This can add a new dimension to the sound that is not heard on many synthesizers, especially when the oscillators are synched or cross modulated.
The strange shaped bender has a mode that I love: If put in LFO mode, then moving it forward changes the amount of LFO to the pitch/frequency of the oscillator. If moving it backward, it modulates the oscillator with the noise source.