Motorola Scalatron Mark 1, courtesy of Wayne Holmes
A keyboard instrument created by the electronics manufacturer Motorola in the mid-1970s. The outstanding feature of the Scalatron was its ability to play in alternate tunings and microtonal intervals. Original development was done by Herman Pedtke and Motorola engineer Richard Harasek, who convinced Motorola management to set up a spin-off, Motorola Scalatraon Inc., to design and build the instrument. It is the only musical instrument ever produced by Motorola.
The Mark 1 Scalatron[]
The original model consisted of a two-manual console, with standard-looking piano-key manuals, and a control panel, in the style of an electric organ of the 1970s. For each manual, the conventional 12 tones of the octave could each be tuned to a desired pitch over a wide range; higher and lower octaves then followed the pattern. This gave the instrument a total capability of 24 tunable tones (12 for each manual).
Sound generation employed a divide-down architecture. A master oscillator running at a stated frequency of 3.5 MHz was divided by a binary counter, one for each of the 12 tones. The user could set the low 10 bits of the counter to a desired value, to produce the desired pitch, over a range of about 200 Hz. Apparently, the counter had non-user-settable upper bits that determined the upper and lower range boundaries for each tone. These dividers produced square waves as their outputs; no other waveforms were available. A printed table that came with the instrument told the user what counter values to use for a desired frequency for each tone. A separate tuner unit, which presented tunings as interference patterns on a video monitor, was also available.
(Doing the math, it appears likely that the master oscillator frequency was actually 3.579545 MHz. Why this value? This was the frequency of the color subcarrier signal in the NTSC analog television system. At the time, Motorola was a leading manufacturer of televisions in North America, and it produced these color subcarrier oscillators by the thousands. The Scalatron project likely simply used this as an off-the-shelf assembly.)
The voice architecture of this version of the Scalatron is usually described as being typical of an electric organ of the era. Likely, the mixed square waves were fed into sets of fixed filters to imitate different types of instrument sounds, as selected by pushbuttons or tabs. As befitting a device that was basically an organ, it was fully polyphonic.
The Mark 2 Scalatron[]
Scalatron Mark 2, courtesy of EMEAPP
In 1974, microtonal composer George Secor attended a demonstration of a Mark 1 Scalatron, and while he was impressed by the instrument's capabilities, he felt that the conventional piano-style keyboard was not the ideal user interface. He worked with Motorola's Harasnek and Don Ryon to design and incorporate a keyboard that would be more suitable. In the process he inadvertently re-invented the 19th-century Bosenquet "generalized keyboard", which has multiple columns of keys allowing microtonal intervals to be played. Banks of DIP switches allowed the tuning for each key to be set individually. An option provided a sort of tuning table memory that held 10 tuning maps.
Secor also pushed Motorola to improve the timbral capabilities of the instrument and give it more synthesizer-like capabilities, including (judging from extant recordings) an envelope generator and VCA for each note, and a LFO that can modulate the master oscillator or the filters. As the Secor keyboard has 280 keys, it is not clear if this version of the instrument is fully polyphonic, since such would require considerable more circuitry.
Production[]
The most reliable sources indicate the Motorola produced 17 of the Mark 1 Scalatron, and three of the Mark 2. It appears that all three of the Mark 2 units had differences. One has a different key layout from the other two. One has, in place of the synth controls, a large array of banana jacks whose purpose is unclear. One has three expression pedals. The last unit was produced in 1981 or 1982.
The University of Melbourne has a Mark 1 unit. The Electronic Music Education and Preservation Projection (EMEAPP) museum in Pennsylvania has two of the Mark 2 units, including the one with the banana jack array.
Acknowledgements[]
Material from this article sources 120years.net and the Microtonal Encyclopedia.