General Terminology

**Signal** – the audio waves generated by the instrument, and later modified by amplifiers, effects, etc. Electric guitar signal is generated (induced) by the strings moving within the magnetic field of the pickups. Every part of the signal chain after the pickup is degrading the signal before the audio wave arrives at the target.

**Noise** – undesired parts of a signal. Example: Single coil pickups are susceptible to 50 or 60 Hz noise or “hum” due to the AC electricity supply. Thus, the evolution to ‘hum-buckers’ to reduce/eliminate that noise. Noise filters and suppressers help with this as well. Balanced audio cables can help with this issue as well, particularly on long runs of cable.

**Frequency** – A measure of how many waves in the signal occur per unit of time. Hertz, or cycles per second, are the standard measurement. Human ability to hear audio waves is typically 20 to 20,000 Hz. Guitar standard tuning is Low E = 82.41 Hz, High E = 329.63 Hz, 24th fret of high E 1318.52 Hz. Typical guitar cabinets are capable of 80-8000Hz. Frequencies outside this range will sound strange coming from a guitar rig.

**Octave** – Double or Half of the original frequency. Standard tuning open A string is 110Hz, and at the 12th fret it is 220 Hz. Called an octave because most scales include 7 notes, the 8th note being double the original frequency.

**Overtones** – Frequencies above the fretted note in the signal. Often, they are octaves above.

**Bass** – Lower frequencies 16-256 Hz is common. Notably, this is the range for the base note for about half of the fretted notes on a guitar.

**Middle** – Frequency band in between or overlapping with Bass and Treble. This is a broad term.

**Treble** – Higher frequencies. Typical for guitar applications seems to be above 2000 Hz. Notably, this is above the highest frequency of a fretted note. This controls overtones of the signal.

**Presence** – Typically controls highest frequencies in the signal. Sparkle, crispness, or clarity. Exactly how the control happens depends on the equipment – some have negative feedback reducing or eliminating certain frequencies.

**Equalization/EQ** – The modification of the signal by adjusting frequency bands. Minimally can be ‘Tone’ control, Bass and Treble control, or multiple specific frequency bands.

**Q** – Width of a frequency range for EQ boost/reduction – shaped like a bell curve. Lower is wider, zero essentially flat. Higher is narrower, almost a spike. The width is then centered on a specific frequency. Example of a mid-boost: Q=0.6, Freq=~900 hz, Boost=~6dB.

**Flat** – basically no frequency adjustment. This is a broad term. “Transparent.”

**Scooped** – Bass and Treble frequencies elevated. This is a broad term.

**Mid-focused, Mid-hump** – Many overdrive pedals elevate the middle frequencies, which works well to fill out the frequency range with Scooped amps, like most Fender-style amps. The Ibanez Tubescreamer is a classic example.

**Amp** – Emulated effect on frequency spectrum and distortion from a model of guitar amplifier. Real amps boost the power of the signal to drive a passive speaker, and this whole system created a lot of the beloved guitar ‘tone.’ Typically, a preamp section increased the signal to be able to equalize the frequencies better, and then a power amp section would boost the signal to drive the speaker.

**Cabinet** – Emulated effect on frequency spectrum and distortion from models of speakers in boxes. Factors such as number of speakers, size of cabinet, size of speaker(s), model of speaker(s), and even construction of the cabinet effect the ‘tone.’ This is then also recorded with a microphone placed in front of the cabinet, and the placement and model of microphone go into this also.

**Impulse Response (IR)** – More detailed emulation of speaker cabinet recording. Uses recordings from specific set ups (amp, cab, speaker, microphone(s), placement) across the audible frequency range to better recreate the entire guitar amplifier experience.

**Gain/Drive** – Typically the control for distortion/clipping of the signal. In some amplifiers Gain is controlling the amplification (volume) of the signal, which is a more general audio processing definition of gain.

**Volume/Master** – Increased amplification of the signal. In some amplifiers this is a true gain control, meaning that more distortion will occur as the control is increased. In others, this control will not affect distortion and only increase the amplification.

**Tone** – In effects or amplifiers, a crude equalization control. Often the higher the tone the more low-end frequencies are reduced, or high frequencies are amplified, leading to a brighter sound. One notable exception is the EHX Big Muff pedals, and as emulated in the Tri Fuzz block. On instruments, the tone knob at maximum is unaffected signal, and reducing the tone knob reduces higher end frequencies.

**Distortion/Clipping** – When an amplifier attempts to produce a voltage it can’t, and the signal wave appears ‘cut off’ at the top and/or bottom. Distortion adds sustain and compresses the signal too. The way in which the signal is clipped effects the sound of the distortion. Subjectively, distortion effects are higher levels of distortion.

**Breakup** – The beginning of distortion in the range of an amp or effect. Subjective.

**Overdrive** – Lower levels of distortion. Subjective.

**Fuzz** – a style of distortion that sounds ‘fuzzy’. The line between distortion and fuzz is subjective. At some point, the harmonic overtones are the dominant part of the signal.

**Feedback** – For guitar, when the sound from the speaker induces harmonics on the strings. Similar to sustain.

**Sustain** – Played notes will decay or reduce volume over time. Sustain is the prolonging of the note, or opposite of decay.

**Headroom** – An amount of signal amplification before there is clipping and distortion.

**Clean** – Typically high Headroom and mostly or totally unaffected signal. In an amplifier, this may still have a modified frequency equalization.

**Wet** – A description of how much an effect is added to the signal. Full wet may be either no original signal, or equal between the effected and original signal. Often used with Time-based effects and Modulation effects.

**Dry** – The original signal, no effects. Can also be described as clean.

**Compression** – Compressors limit the difference between the quietest and loudest parts of a signal.

           -Threshold – Minimum signal strength where the compressor will take effect

           -Knee – Shape of compression. Smooth knee is a more gradual effect. Hard is abrupt.

           -Attack Time – Time before the signal is fully compressed

           -Release – Time for signal to fully decompress. Make it low, but more than attack time.

           -Ratio – Compressed signal compared to original signal strength.

- 1:1=No effect, 20:1=Almost flat

           -Output Gain – Makes up gain of signal in compression process

**Time-based Effects** – Reverbs and Delays, also Looping.

**Expression Effects** – Variable sweep of one or more parameters of an effect. It’s a control knob that can be moved with a foot. Wah and Volume are common.

**Reverb** – Actual or emulated reflection of sound waves off surfaces surrounding a sound source. Spring and Plate reverbs are guitar signals running through springs (‘tanks’ in a physical amplifier/cabinet) and large plates in recording studios. Digital reverb (all HeadRush models) is a digital emulation of these effects.

**Delay Effects/Looping** – Repeating a recorded sound. The duration of the recording, mix of the recording to dry signal, decay of repeats, and any effect added to the recording enhance the effect. Delay is typically in the 0-400ms range. Looping is a recording that is repeated, but typically longer recordings (over 1 second), like musical phrases. Most delay is done with digital recording. Original delay effects were recorded on tape and replayed. The tape inconsistency is now a desirable effect and can be digitally emulated. Division in delay is the fraction of the set tempo that automatically adjusts the delay time to sync with the tempo.

**Tap Tempo** – When the time of a delay or modulation effect can be input by tapping a footswitch to align with the tempo of the song.

**Sync** – For Headrush, when an effect is aligned with the tempo designated in the rig.

**Tails** – When an effect is turned off, the repeats or “tails” of the effect can continue their decay, rather than stopping abruptly.

**Ducking –** Initial delays are reduced in volume to maintain clarity of the original signal.

**Pre-Delay –** Similar to ducking, a reverb effect is initially reduced or eliminated initially to maintain clarity of the original signal.

**Modulation Effects** – Chorus, Vibrato, Phaser, Flanger, Tremolo, Pitch Shifters and Rotary Speaker effects.

**Vibrato** – Effect that subtly changes the frequency (pitch) of the signal up and down repeatedly. Gives a sea-sick type of sound if the effect is intense. Some Fender style amplifiers include an effect with this name, which is technically the Tremolo effect.

**Chorus** – A mixture of Vibrato with dry signal.

**Tremolo** – Effect that varies the volume of the signal up and down repeatedly. Incorrectly used to describe vibrato bridges on guitars, which changes the frequency of the signal. One key characteristic is the shape of the effect. Square is very abrupt and choppy, Sine wave is very smooth and less noticeable at low depth and rate. Triangle is somewhere in between those two and is the most common, at least in HeadRush.

**Phaser** – Phasing is a variable frequency sweep at multiple frequencies, mixed with a dry signal. Phasers typically have multiple frequency filters that move (oscillate) over a section of frequencies. Controlling the depth of the frequency effect, the rate of the oscillation (LFO) and the mix of wet and dry are the key parameters. Sometimes there is a feedback loop that sends part of the output signal back into the effect again. Due to the high number of variables in this effect, each circuit design can produce significantly different sounds. This effect is not phase inversion.

**Flanger** – An oscillating micro-delay that feeds back on itself. This wet signal is then mixed with dry signal.

**Rotary Speaker** – There are cabinets with rotating speakers in them, and a stationary microphone, giving a ‘whoosh’ type sound, kind of a mix of modulation effects into its own thing. In the HeadRush, there are various emulations of classic versions/uses of these effects.

**MIDI** – For this use, it’s a format that allows changes to occur on the device by using another device. This can be as simple as an external footswitch changing a single parameter, or more complicated by changing multiple parameters at once. MIDI has other applications as well.

**Stereo (Width)** – The signal has two separate channels to right and left. Width is, in a way, the amount of difference between the two channels. Zero width is the same as a mono signal, and 100% width is two entirely separate channels – Ping Pong delay and stereo headphones is a great way to hear this effect.

Further Resources – After developing this section, https://www.sweetwater.com/insync/category/glossary was discovered to have a lot more definitions available. However, not all of them are specific to Guitar, Bass, or HeadRush.