GLOSSARY ANTI-ALIASING Anti-aliasing is the removal of aliasing interference. Aliasing occurs in digital systems when the frequency of the note increases (high notes are affected most). Anti-aliasing takes up more CPU speed, but improves the sound quality. DISTORTION Distortion is an effect which amplifies the input signal but prevents it from going above a certain level. This clipping gives an extra edge to the sound. AXS has two types of distortion; loud and soft. ENVELOPE An envelope is an element with time-varying output which modulates another synthesis parameter like volume, pitch or filter cutoff frequency. The goal of envelopes is to give precise control over how ie. the amplitude varies over time from the moment a new note is played. There are several types of envelopes. The type used in AXS is the ADSR-envelope. The letters ADSR represent the four stages of this envelope. ![]() 'A' stands for 'Attack (time)' and controls how long it will take the envelope output to go from 0 when a new note is started to its maximum output level. 'D' stands for 'Decay (time)' and controls how long it will take the envelope output to go from its maximum level (after finishing the attack phase) to the sustain level. 'S' stands for 'Sustain (level)' and controls at which level the the envelope will remain after finishing the attack and decay phase. 'R' stands for 'Release (time)' and controls how long it will take the envelope output to go from its current (sustain) level to 0. The release phase is started when you release a key. FILTER A filter is generally something which rejects certain elements and lets through other elements. In the audio field, filters are used to reject certain frequencies from a signal. A filter which rejects high frequencies and lets through low frequencies is called a low-pass filter. A filter which rejects low frequencies and lets through high frequencies is called a high-pass filter. The frequency at which the filter changes from pass to non-pass is called the filter cutoff frequency. A band-pass filter lets through a specified band of frequencies. Frequencies not in this band are removed. A band-reject filter removes a specified band of frequencies. In the case of a band-pass/reject filter, the filter cutoff frequency defines the centre of the band. FILTER KEYBOARD TRACKING Filter keyboard tracking is the process in which the filter cutoff frequency is altered depending on the note you play. If this is set to 0, the filter cutoff frequency will be independant of the note you play. If this is 1, the filter cutoff frequency will be increased by 1*note frequency. AXS has 0/3, 1/3, 2/3 and 3/3 * keyboard tracking. Filter keyboard tracking will cause presets to sound more constant over range of keys. FREQUENCY Frequency is the mathematical name for how often something occurs every second. For example, the seconds-indicator of your watch is updated once every second, so it has a frequency of 1 Hz (Hertz). The minute indicator is updated once every 60 seconds, so it has a frequency of 1/60 Hz. In the audio field we're often working with high frequencies. For example a CD reads data 44100 times a second (44100 Hz). A mathematician called Fourier figured out all audio signals can be constructed from a huge amount of sine-waves each at a different frequency. When we refer to 'a frequency' we will mean 'a fourier frequency component'; a sine-wave at that frequency. KEYBOARD-TRACKING Every note on a keyboard has its corresponding frequency. With keyboard tracking enabled, a key's frequency is also the frequency used by the oscillators. With keyboard tracking turned off, the note you play will have no effect on the frequency of the oscillators. LFO LFO stands for Low Frequency Oscillator. An LFO is identical to any other oscillator except it operates at lower frequencies (0..40 Hz). Another difference between oscillators and LFO's is that the output of an oscillator is used as an audio signal, while the output of an LFO is used to control other synthesis parameters, like amplitude, pitch, etc. LFO SYNC LFO synchronisation restarts the LFO shape whenever a new note is played. With LFO sync turned off, the LFO runs freely. When a new note is started, the current LFO output will be used. With LFO sync enabled, every new note will restart the LFO. MIDI MIDI stands for 'Musical Instrument Digital Interface' and is the only real hard- and software standard for the communication between musically orientated digital hardware. AXS is fully MIDI compliant to guarentee optimal compatibility with existing MIDI hardware. CHANNEL/MIDI CHANNEL, PART/MIDI PART A part, a MIDI part, a channel and a MIDI channel are all the same things. The MIDI standard describes how 2 MIDI devices can be connected to eachother. This connection is made with a MIDI-cable. The MIDI standard supports 16 channels for every cable. Each channel can be set up to play a different sound, have a different volume, etc. So this allows 16 sounds to be controlled over a single cable. MIDI CONTROLLER MIDI Controllers are devices which send out MIDI control change messages. These control changes affect parameters of the sound synthesis process. So for example MIDI controller 74 is connected to the filter cutoff amount. And MIDI controller 10 is the MIDI channel volume. MIDI PRESET The first (monophonic) analogue synthesizers had a one-on-one interface. So there was only one voice and every knob on the synth was directly coupled to the synthesis parameters. To reconstruct a previous sound, all knobs had to be set to their correct setting. To remember the settings of a sound there were preset charts on which all knob positions could be noted. The digital equivilant of this is pressing a button to select a new 'preset' which causes all the knobs on screen to take in their new position. OSCILLATOR An oscillator is an element which produces an output signal at a constant frequency. In the analogue synthesizer field, oscillators produce basic shapes like sine, triangle, saw, block/pulse and noise. OSCILLATOR SYNC In AXS, OSC2 can be synchronised to OSC1. This means every time OSC1 restarts its shape, OSC2 will also be restarted. When both oscillators are set to the same frequency, sync will have no effect. When OSC2 is set at a higher frequency than OSC1, more than one OSC2 shape will be generated before the OSC2 shape is re-synced. When OSC2 is set at a lower frequency than OSC1, less than one OSC2 shape will have been generated when OSC2 is re-synced. PITCH Pitch is the human perception of frequency. When we listen to an instrument it can contain loads of frequencies ('fourier frequency components'), but humans will hear the sound at a certain pitch. (for example C#). The study of how humans determine the pitch is very complicated and is part of the psycho-acoustics study. RESONANCE Resonance is a naturally occuring process in which an element oscillates. For example when you pluck a guitar-string, the string will continue to resonate after you have released it. Eventually the string stops resonating due to natural losses. In the electronic music industry, resonance is often associated with filter resonance. Like the guitar-string, a digital filter can resonate. So after the input has stopped, the filter will continue to produce output for some time. Speaking in frequency-terms, a renonant filter can enhance certain frequencies (a standard filter will only pass/reject frequencies). So be careful when using high resonance values, as the resulting sound has a much greater volume. REVERB The reverb or reverbration effect adds a natural spaceousnes to the sound. In everyday life, all sound we hear is a combination of direct sound (ie. from a breaking glass) and indirect sound (sound reflecting from the ceiling and walls). Without this indirect sound everything would sound like it was played in mid-air with no objects to reflect the sound. RINGMODULATION A ringmodulator takes 2 input signals and combines them to create a new audio signal. Ringmodulators add a mettalic touch to the sound. AXS has two types of ringmodulator. |