For the enlightened amateur of the 70s, entry into the fabulous world of synthesizers necessarily begins with a… monophonic. As its name suggests, a monophonic instrument is capable of emitting only one sound at a time, or rather, a sound vibrating on a single frequency. This is also the case for acoustic instruments such as the trumpet, the saxophone, the oboe, etc. In the case of the synthesizer, the choice of monophony was long due to a technological limitation: basically, the synthesizer is made from a single oscillator, which generates an electrical frequency. This frequency then undergoes a series of adjustments and transformations (via envelopes, filters, etc.) to result in a musical signal. Playing several notes, of different frequencies, at the same time (in polyphony, therefore), involves multiplying the oscillators. In the pioneering days when Robert Moog created his first model, this would have been far too expensive, even for the wealthiest musician.

But what may initially seem like a limitation has instead made the monophonic synthesizer an instrument in its own right. Indeed, we do not approach a monophonic instrument and a polyphonic instrument in the same way: the role of the monophonic synthesizer is to « place » itself in the music, for example within the framework of a melodic line (or a bass line), while a polyphonic instrument will have more of a rhythmic or harmonic role. Thanks to this characteristic, the monophonic synthesizer has pushed musicians to make it the king in terms of solos, themes, and sound effects… you only have to listen to the « antics » of Rick Wakeman on his Minimoog or Keith Emerson on his modular to be convinced. And, if we want to go back a little further in time, the French ancestor (and with tubes!) of the synthesizer, the « ondes Martenot », also monophonic, was used for similar functions (imitating the human voice for example). »