The rhythm machines found on this website all generate analog sounds; the different percussion voices are not samples, they are generated electrically through discrete components. Sometimes, a primitive CPU is used to store the various beats available, or to record and playback a sequence, but this digital circuitry is not related to the actual sound generation, only to note triggering and pattern memory.
Most of the time, these “drum” sounds really don’t sound anywhere near a real percussion instrument: a cymbal sounds like a burst of white noise, a tuned tom sounds like a mono-synth… Which is what makes these machines so unique and interesting, as long as one doesn’t expect to reproduce the natural tone of real percussion instruments, but instead focus on the qualities as synthetic sounds.
The most primitive, sixties drum machines were designed to accompany organ players, and are usually comprised of tempo, tone & volume knobs, a few buttons to select preset rhythms, one output for all sounds and an on/off foot switch jack. Some of them are attached to amplifiers and cabinets, making them big and heavy. Often, it is possible to combine more than one rhythm by depressing two or more preset buttons at the same time, which can lead to interesting variations. The early Ace Tone Rhythm Ace units, designed by Roland founder Ikutaro Kakehashi, are a good representative of such machines.
Next generation rhythm machines added features such as a variation (for example, a short roll or break every 2,4,6 or 8 bars, or automatic switching between two beats), an accent knob to vary the volume of certain hits, tuning capabilities for the various voices, and the ability to turn on/off or adjust the volume of specific voices. The Korg Mini-Pops, Rhythm 55b and Yamaha MR-10 are such machines.
In the late seventies, the Roland CR-78 was launched, allowing users to program their own rhythm. This was a critical advance in the technology of rhythm machines, and paved the way for perhaps the most famous analog drum machines of the eighties, the Roland TR series (the TR-808 being the most well known). Other early programmable drum machines from this era are the Roland CR-8000 and the Korg KPR-77.
As is the case for many other audio technologies, the peak of quality, features and design for analog drum machines was reached in the early/mid eighties. Not long after that, analog synthesis was replaced by digital drum sounds, most notably in the shape of drum samples, the quality of which has been improving throughout the years.
Nowadays, it is possible to program drum sounds that can sound very similar to real drums, leaps beyond early analog units’ attempts at emulating a drummer. Niche market analog drum boxes complimented with digital circuitry for programming, preset recall, etc. are still being manufactured as well.
One of the most common modifications to early analog drum machines is to separate some of the drum sounds, in order to be able to mix and process them independently. This can be done relatively easily, or is sometimes more complex, depending on the device. Furthermore, in some cases sounds are hardwired to the same tone generators (most notably noise generators used for early cymbal and snare sounds), making them impossible to separate. Many units on this website have been modified for separate outputs, to be then used for ESTECHO tracks.