Electronic Music Instuments
There are lots of details to cover in an exhaustive explanation of musical synthesizers. You will not, at least for now, find that here. Instead you can find here a unique perspective of some the more interesting aspects of synthesizers. To fully apreciate what follows it is expected that you have a general understanding of sound, music, musical instruments and electronics. However, links to subjects that are glossed over or assumed in the explanations will have a link provided to a more detailed explanation for further details.
A synthesizer is a musical device that emulates other musical devices and can create entirely new sounds that no other instrument can make. Earlyexamples of synthesis is the pipe organ or read organ. Organs shape the sound by combining several fundamental notes. That is the fundamental root note has additional harmonics added to it manually by the musician. These controls that mix differently pitched fundamental notes are called manuals (they are also called stop). It is the combination of different fundamentals that approximates different accoustic instruments. The tonal charactersitic between instruments is the unique assortment and volume of notes that comprise it. Since these organs predate the use of elctricity so they are non-electronic synthesizers.
But what differentiates one acoustic instrument from another is more than just its tone. There is also the attack, decay, sustain, and release of each note played on the isntrument. But more on this ADSR latter.
The old pipe organ was a type of addative synthesizer. Another type of synthesizer that starts with an already complex wave form rich with overtone (harmonics) and shapes the sound with filters by removing compnants of the complex waveform is called a subtractive synthesizer.
Componants of modular synthesizers.
Oscillator
An oscillator is any device that produces a repetitious pattern. In a saxaphone the reed oscillates when it is placed in the musicians mouth and blown. On a guitar the strings oscillate when plucked. In electronic music there are a variety of ways to produce and electronic oscillation but they are generaly simple devices that produce either a sine, square, triangle, or sawtooth wave. Generally they have no controls expcept for pitch, and wave form selection.
Amplifier
An amplifier is used to change the volume of th wave the oscillator produces. A device that works closely with or sometimes in place of an amplifier is a special type of amplifier which has multlple temporal stage. This device is called an evelope generator.
Controller
The controller usually takes the form of a keyboard and controlls the pitch of the oscillator and the switching on and off of the amplifier/envelope generator
Filter
Various filters can be used to remove various frequencies or range of frequencies from the signal created by the oscillator. Filters can also be used to selectiely amplify spcified frequencies. Some kinds of filters can be operated to self resonate and act as an additional oscillator.
Envelope Generator
The evelope generator can be thought of a group of amplifiers arranged temporarly with regards to the trigger or gate signal sent from the controller. Generally there are four stages to an envelope: The Attack, Decay, Sustatain, and Release. The attack is a durration control that determines the ammount of time an oscillator signal takes to gofrom no volume to full volume after the controller triggers the envelope. The Decay is the time it takes for the oscillator signal to be attenuated to the Sustatain level after the End of the attack durration. The sustain level is the volume level that will be maintain after the Attack and Decay and as long as the controller key is depressed. The Release is the durration that the oscillator signal takes to be turned to zero from the sustain level after the contrller's key is released.
Modulation
Modulation generally refers to using a low frequency oscillator to modify the pitch, volume, of filtration of the main oscillators signal. The result is vibrato, tremelo, or chorus effect. Combinations of modulation create unique sounds to electronic music.
Sequencer
A sequencer is essentially a clock that controlls a series of switches that can be assigned to controll the oscillator, Envelope Generator, various filter parameters, modulators or whatever. A simple example of a sequencer is four switches: The first on turns on and then after one second turns off while simulatneously the second switch turns on. After one more second the second switch turns off while simultaneously the third swtich turns on. After one more second the third switch turns off while simultaneously the Fourth swtich turns on. Finally after one more second the fourth switch turns off while the first switch tuurns back on and starts the cycle over again. These switched can essentially be assigned a specific key on the controller and so could play a repeating sequence of four notes over and over. The clock speed contrlling the switches can be spead up or slowed down. Eights step and sixteen step sequencers are common. And sequencers can be used to control additinal sequencers to produce vary ellaborite patterns of controlls. A more recent development of sequencers takes the form of a controller recorder, where the controller is played and the sequencer records the keys pressed and the start and stop times of each key depression. This type of sequencer has a vary dfferent interface than that of the previous type of sequencer discussed and may more rightly be called a controller recorder.
Other
Portamento (glide or glissando) is the effect sliding between notes. Controllers can be equiped to create this effect with playing all the notes between by use of a single Glide control which can be used to vary the glide speed between to notes from zero (essential off) to a durration as long a second or more for some types of contrllers.
Pitch bend is an additional controller found on keyboard controllers that allows the musician to change the pitch of a note after depressing a key. The amount of pitch bend up or down can be varied and used for glissando effect or vibrato.
There are numerous other type of controls and methods of altering the sound of an oscillator but the above list provides the most common modules of synthesizers.