disco, often combined with elements of Indian music. Biddu had already used electronic equipment such as synthesizers in some of his earlier disco work, including "Bionic Boogie" from Rain Forest (1976), "Soul Coaxing" (1977), Eastern Man and Futuristic Journey (recorded from 1976 to 1977), and "Phantasm" (1979), before using synthesizers for his later work with Nazia Hassan, including "Aap Jaisa Koi" (1980), Disco Deewane (1981) and "Boom Boom" (1982). Bollywood disco producers who used electronic equipment such as synthesizers include R.D. Burman, on songs such as "Dhanno Ki Aankhon Mein" (Kitaab, 1977) and "Pyaar Karne Waale" (Shaan, 1980); Laxmikant–Pyarelal, on songs such as "Om Shanti Om" (Karz, 1980); and Bappi Lahari, on songs such as "Ramba Ho" (Armaan, 1981). They also experimented with minimalist, high-tempo, electronic disco, including Burman's "Dil Lena Khel Hai Dildar Ka" (Zamane Ko Dikhana Hai, 1981), which had a "futuristic electro feel", and Lahiri's "Yaad Aa Raha Hai" (Disco Dancer, 1982). Such experiments eventually culminated in the work of Charanjit Singh, whose 1982 record Synthesizing: Ten Ragas to a Disco Beat anticipated the sound of acid house music, years before the genre arose in the Chicago house scene of the late 1980s. Using the Roland TR-808 drum machine, TB-303 bass synthesizer, and Jupiter-8 synthesizer, Singh increased the disco tempo up to a "techno wavelength" and made the sounds more minimalistic, while pairing them with "mystical, repetitive, instrumental Indian ragas", to produce a new sound, which resembled acid house. According to Singh: "There was lots of disco music in films back in 1982. So I thought why not do something different using disco music only. I got an idea to play all the Indian ragas and give the beat a disco beat – and turn off the tabla. And I did it. And it turned out good." The first track "Raga Bhairavi" also had a synthesised voice that says "Om Namah Shivaya" through a vocoder. Along with experiments in electronic disco, another experimental trend in Indian disco music of the early 1980s was the fusion of disco and psychedelic music. Due to 1960s psychedelic rock, popularised by the Beatles' raga rock, borrowing heavily from Indian music, it began exerting a reverse influence and had blended with Bollywood music by the early 1970s. This led to Bollywood producers exploring a middle-ground between disco and psychedelia in the early 1980s. Producers who experimented with disco-psychedelic fusion included Laxmikant–Pyarelal, on