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5.14 sfxr

sfxr is a port of the original sfxr tool. It is used to generate retro video game sounds.
Please note that volume level of the sounds generated by sfxr varies quite a bit, especially with the RAND button.

5.14.1 Generator

The easiest way to use sfxr is with the generator tab in the top right corner. In this box are two large text buttons and seven smaller buttons. Text Buttons

The RAND button, short for random, generates a completely random sound effect. Because of this, it can generate all kinds of sounds, from cool to boring, and even completely silent ones. To the right of it is the MUTA button, short for mutate. This is similar to randomizing, but instead tweaks your current sound a bit. It's useful to generate variations on a sound, or change a sound slightly to (hopefully) make it better. Icons

Underneath the RAND and MUTA buttons are seven icons. These each represent presets that sfxr uses to generate a specific type of sound. In order, they are:
  • - Coin/Money pickup
  • - Shooting
  • - Explosion
  • - Powerup
  • - Damage
  • - Jump
  • - Interact
These generate a wide variety of sounds, while still managing to be recognizable. This is where sfxr really shines.

5.14.2 Controls

There are also several controls that can be used to tweak a generated sound, or to create on from scratch. To the left of the generator tab are the available waveforms (
). Below this are several knobs for changing other parameters. Envelope

The top knobs are labeled Env., short for envelope, and are bordered by, and connected with, blue lines. They decide how the volume of the sound changes over time. ATT, or attack, determines how long it takes for the sound to reach maximum volume. HOLD is how long the sound stays at this level. SUS, short for sustain, is how loud the sound gets at the start. Finally, DEC, or decay, is how long it takes for the sound to fade out. Frequency

Underneath the envelope knobs are the green Freq. knobs, which control the frequency of the sound. START is the start frequency, and MIN is the minimum frequency. SLIDE makes the sound change frequency over time, with a positive number making it go up, and a negative number making it go down. D.SLI., or Delta slide, affects how fast the frequency changes. Values closer to 1 or -1 make the frequency change faster, while values closer to 0 make it slower. A negative value reverses the slide, making an upwards slide go downwards and vice versa. V.DEP., or vibrato depth, changes how much of an effect vibrato has, while V.SPD., or vibrato speed, changes how fast the vibrato is. Change

In the middle and on the right of the knobs are two red knobs, labelled Change. C.AMT stands for change amount, when you have positive values, the note will at a point, decided by the C.SPD - change speed or suddenly jump to a higher frequency. If you set the knob to negative values the new frequency will be lower than the original. This new frequency will last for as long as the note is held. Change amount set to 0 doesn't affect the sound. Change amount set to 0.25 raises the tone with one semitone. Change amount set to 1 raises the tone with 3 octaves and 4 semitones. The Change speed takes the note frequency in consideration on it's calculations, a low frequency note plays the original note longer before jumping to the new frequency than a high note does. Even if change speed is set to 0, the note will jump. Square

In the middle and on the left of the knobs are two orange knobs with options for when a square wave is used, labelled Square. S.Duty changes the duty cycle, shifting the lowest parts of the square wave up, while S.SPD changes the duty cycle over time in a sweep. Repeat

Under the middle and on the left of the knobs is a section called Repeat, with only one grey knob, R.SPD. or repeat speed. Setting this knob to anything other than zero will play the sound twice, with a slight delay in between. The higher the value, the shorter the delay. Phaser

Under the middle and to the right is a section labelled Phaser, with two silver knobs. PH.OFF. or phaser offset, and PH.S. or phaser sweep. A phaser combines a signal with an offset version of itself, leading to phase cancellation in some frequencies. In practical terms this leads to a shifting filter effect. Filter

All the way at the bottom, there are five purple knobs, labelled Filter. The ones that start with L are low pass filter settings, and the ones that start with H are high pass filter settings. LF.C. and HF.C. are low pass cutoff and high pass cutoff, respectively. On a low pass filter, frequencies below the cutoff are dampened. LF.S. and HF.S. are low pass sweep and high pass sweep. Positive values increase the filter cutoff with time (lowering it for low pass and raising it for high pass), and negative values decrease it, with numbers further from zero changing the cutoff more. Finally, the low pass filter has an additional resonance knob, LF.R., to increase or decrease resonance. With resonance, frequencies near the cutoff point are boosted.