convinced Katoh to finance his efforts to build a better one. In 1963, their new company Keio-Giken (later Korg) released their first rhythm machine, the Donca-Matic DA-20, using vacuum tube circuits for sounds and a mechanical wheel for rhythm patterns. It was a floor-type machine with a built-in speaker, and featured a keyboard for manual play, in addition to the multiple automatic rhythm patterns. Its price was comparable with the average annual income of Japanese at that time. Next, their effort was focused on the improvement of reliability and performance, along with size and cost reductions. Unstable vacuum tube circuits were replaced with reliable transistor circuits on the Donca-Matic DC-11 in the mid-1960s. In 1966, the bulky mechanical wheel was also replaced with a compact transistor circuit on the Donca-Matic DE-20 and DE-11. In 1967, the Mini Pops MP-2 was developed as an option for the Yamaha Electone (electric organ), and Mini Pops was established as a series of compact desktop rhythm machines. In the United States, Mini Pops MP-3, MP-7, etc. were sold under the Univox brand by the distributor at that time, Unicord Corporation. In 1965, Nippon Columbia filed a patent for an automatic rhythm instrument. It described it as an "automatic rhythm player which is simple but capable of electronically producing various rhythms in the characteristic tones of a drum, a piccolo and so on." It has some similarities to Seeburg's slightly earlier 1964 patent. In 1967, Ace Tone founder Ikutaro Kakehashi (later founder of Roland Corporation) developed the preset rhythm-pattern generator using diode matrix circuit, which has some similarities to the earlier Seeburg and Nippon Columbia patents. Kakehashi's patent describes his device as a "plurality of inverting circuits and/or clipper circuits" which "are connected to a counting circuit to synthesize the output signal of the counting circuit" where the "synthesized output signal becomes a desired rhythm." Ace Tone commercialized its preset rhythm machine, called the FR-1 Rhythm Ace, in 1967. It offered 16 preset patterns, and four buttons to manually play each instrument sound (cymbal, claves, cowbell and bass drum). The rhythm patterns could also be cascaded together by pushing multiple rhythm buttons simultaneously, and the possible combination of rhythm patterns were more than a hundred (on the later models of Rhythm Ace, the individual volumes of each instrument could be adjusted with the small knobs or faders). The FR-1 was adopted by the Hammond Organ