Synthesis

In music technology, sound synthesis is the process of generating or creating sound from analogue and digital equipment, often for musical, artistic or entertainment purposes. In particular, sound synthesis refers to the process of the creation, combination or mixing of sounds from a set of routines in order to create sounds of a greater complexity and richness. Sound synthesis can be used to mimic acoustic sound sources or generate sound that may be impossible to realise naturally.

When any mechanical collision occurs sound is produced. The energy from the collision is transferred through the air as sound waves, which are perceived by the human auditory system. Sound waves are the aggregate of one or many periodic vibrations, described mathematically by sine waves. The characteristics of a sound, known as pitch and timbre, are defined by the amplitude and pitch of each individual sine wave, collectively know as the partials or harmonics. Generally, a sound that does not change over time will include a pundamental partial or harmonic, and any number of partials. Traditionally, the aims and methods of generating sounds via synthesis is to attempt to mimic the amplitude and pitch of the partials in an acoustic sound source, effectively creating a mathematical model for the sound.

Software Synthesis
A software synthesizer, also known as a softsynth or virtual instrument is a computer program for digital audio generation. Computer software which can create sounds or music is not new, but advances in processing speed are allowing softsynths to accomplish the same tasks as dedicated hardware. Softsynths can be cheaper and more portable than dedicated hardware, and easier to interface with other music software such as music sequencers.

Dedicated hardware synthesizers can have software as complex as a softsynth. The distinction is that softsynths run on a general purpose computer with a sound card, and the hardware (dedicated) synthesizer have the custom software built-in. The advantage to dedicated hardware is that it can be more stable, and also that it often has a user interface that is physical (knobs and sliders) and therefore easier to manipulate during performances. Many softsynths use mathematical algorithms which directly emulate the electronic components and circuitry of the original hardware synthesizer. This results in an exceptionally authentic sound, as well as allowing for some of the inconsistencies, such as oscillator drift caused by the thermal sensitivity of the components, to be added.

One common type of softsynth is an emulator. There are a number of very popular synthesizers which are no longer manufactured. While some can be purchased second hand, many are expensive and temperamental. The emulation can even extend to having graphics that model the exact placements of controls. Some emulators can even import the original sound patches with accuracy that is nearly indistinguishable from the original synthesizer. Popular synthesizers such as the Minimoog and Yamaha DX-7, Korg M1, Prophet V, Oberheim OB-X, Roland Jupiter 8, ARP 2600 and dozens of other classics have emulators.

Some softsynths are heavily sample based. Computers have fewer restrictions on memory than dedicated hardware synthesizers. Some of these sample based synthesizers come with sample libraries many gigabytes in size. Some are specifically designed to mimic real world instruments such as pianos. Many sample libraries are available in a common format like WAV files, and can be used with almost any sampler based softsynth.

It's common for recent softsynths to be compatible with technology such as Virtual Studio Technology (VST), which allow other music software to interface with the softsynth. Plug-in technologies include VST, DXi, Motu Audio System (MAS), Audio Units (AU), and Real Time Audio Suite (RTAS).

Hardware Synthesis
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