#Frequencymodulation synthesis (or FM synthesis)

 is a form of sound synthesis whereby the frequency of a waveform is changed by modulating its frequency with a modulator. The frequency of an oscillator is altered "in accordance with the amplitude of a modulating signal". (Dodge & Jerse 1997, p. 115)  FM synthesis can create both harmonic and inharmonic sounds. To synthesize harmonic sounds, the modulating signal must have a harmonic relationship to the original carrier signal. As the amount of frequency modulation increases, the sound grows progressively complex. Through the use of modulators with frequencies that are non-integer multiples of the carrier signal (i.e. inharmonic), inharmonic bell-like and percussive spectra can be created.  #FMsynthesis using analog oscillators may result in pitch instability. 

However, FM synthesis can also be implemented digitally, which is more stable and became standard practice. Digital FM synthesis (implemented as phase modulation) was the basis of several musical instruments beginning as early as 1974. Yamaha built the first prototype digital synthesizer in 1974, based on FM synthesis,[1] before commercially releasing the Yamaha GS-1 in 1980.[2] The Synclavier I, manufactured by New England Digital Corporation beginning in 1978, included a digital FM synthesizer, using an FM synthesis algorithm licensed from Yamaha.[3] Yamaha's groundbreaking DX7 synthesizer, released in 1983, brought FM to the forefront of synthesis in the mid-1980s.  

FM synthesis had also become the usual setting for games and software until the mid-nineties. Through sound cards like the AdLib and Sound Blaster, IBM PCs popularized Yamaha chips like OPL2 and OPL3. OPNB was used as main basic sound generator board in SNK Neo Geo operated arcades (MVS) and home console (AES). The related OPN2 was used in the Fujitsu FM Towns Marty and Sega Genesis as one of its sound generator chips. Similarly, Sharp X68000 and MSX (Yamaha computer unit) also use #FM -based soundchip, OPM.  An analog (or analogue) synthesizer is a synthesizer that uses analog circuits and analog signals to generate sound electronically.  The earliest analog synthesizers in the 1920s and 1930s, such as the Trautonium, were built with a variety of vacuum-tube (thermionic valve) and electro-mechanical technologies. After the 1960s, analog synthesizers were built using operational amplifier (op-amp) integrated circuits, and used potentiometers (pots, or variable resistors) to adjust the sound parameters. Analog synthesizers also use low-pass filters and high-pass filters to modify the sound. 

While 1960s-era analog synthesizers such as the Moog used a number of independent electronic modules connected by patch cables, later analog synthesizers such as the Minimoog integrated them into single units, eliminating patch cords in favour of integrated signal routing systems.  #synthesizer weki