A sub bass is the deep, felt low end of a track, the part you feel more than hear, roughly the 20 to 60 Hz region and up to about 80 Hz. Making one that works is a few choices done well: a clean sine or triangle for the tone, kept mono and centred, tuned to the key, with the level watched carefully and often a mid bass layered on top so it survives on phones. Here is each choice and how they fit together.
This is about the sub itself, the deep layer that carries the weight, on any synth in any DAW. It usually sits under the rest of the bass rather than replacing it, so it pairs with the broader bass sound.
A sub bass is the deep, felt low end of a track, the energy roughly in the 20 to 60 Hz region and reaching up to about 80 Hz. It is the part of a mix you feel in your body more than you hear as a clear pitch, the weight that sits under a kick and a bassline. Because it is so low, a big system or a good pair of headphones will reproduce it, while most laptops and phones mostly cannot, and that one fact shapes nearly every decision below.
Building a sub is a short chain of choices. You pick a clean waveform for the tone, keep it mono and centred so it stays solid, tune it to the key so it agrees with the music, watch the level so it does not swallow the mix, usually layer a mid bass on top so the note still reads on small speakers, and sidechain it to the kick so the two do not fight. Each of those is a separate decision, and the table below is the map for the rest of this page.
| Choice | What it decides | Rule of thumb |
|---|---|---|
| Waveform | How pure and deep the tone is | A clean sine or triangle, little harmonic content |
| Width | Whether the low end stays solid | Mono and centred, never widened |
| Tuning | Whether it agrees with the music | Match the key, usually the root of the bass |
| Level | How much headroom it uses | Trust a meter and a reference, not your speakers |
| Layering | Whether it reads on phones | A mid bass on top carries the pitch up high |
| Sidechain | How it shares space with the kick | Duck the sub where the kick hits |
One thing to separate early: this page is about the sub, the deep layer on its own. The broader bass sound, the character you actually hear, the oscillator and filter and grit, is a wider job. If that is what you are after, the how to make a bass sound guide covers it, and the sub here usually lives underneath it as one clean layer.
Use a clean sine or a triangle. A sine puts almost all of its energy right at the fundamental with practically no harmonics, which is about as pure and deep as a sub gets. A triangle is nearly as clean with a few faint harmonics, so it reads a touch brighter while still staying mostly sub. Richer waves like a saw or a square carry a lot of harmonic content higher up, which tends to clutter the low end, so they are usually better kept for a separate mid layer rather than for the sub itself.
| Waveform | Character | Good for |
|---|---|---|
| Sine | Pure and round, all energy at the fundamental, no harmonics | The cleanest, deepest sub, the weight under everything |
| Triangle | Soft and mellow with a few faint harmonics, a touch brighter than a sine | A sub with slightly more presence, a little easier to hear |
| Saw or square | Bright and full of harmonics, a lot of energy up high | Better as a separate mid layer on top, not as the sub |
A sub is almost always strongest in mono and dead centre. Low frequencies are hard for the ear to place in the stereo field anyway, and widening the sub can make it thin out or partly cancel when a club rig, a phone or a vinyl cut sums the sound to mono. Keep the sub as a single centred thing and it stays solid everywhere. If you want width and movement in the bass, put it on a higher layer and leave the sub alone.
Because a sub is still a pitched note, it has to agree with the music, so tune it to the key, usually to the root of whatever the bass is playing. An out of tune sub does not read as a clear low note, it reads as a muddy rumble that quietly fights the harmony. Match it to the key first, then worry about tone. If the sub follows the same roots as your bassline, it will sit under the track rather than blur it.
You cannot force low end out of a speaker that has none, so you do two things instead: watch the level so the sub is present without eating the whole mix, and layer a mid-range bass on top that carries the same pitch up where small speakers can actually play it. The sub carries the felt weight on big systems, and the mid layer carries the recognisable note on phones. Together they cover both without either one having to do the impossible.
Sub frequencies carry a lot of energy, so even a sub you can barely hear can be using up a surprising amount of your headroom and pushing the whole mix around. The catch is that you often cannot hear the sub on the speakers in front of you, so judging its level by ear alone is unreliable. Trust a spectrum analyser to see how much is there, and check against a reference track you know sounds right, rather than guessing from a laptop or a small monitor.
The common and reliable approach is two layers. The sub, a clean sine or triangle, carries the deep weight and stays untouched, mono and centred. A second, mid-range bass layer plays the same notes an octave or two up, where it has harmonics a phone speaker can reproduce, so the line is still audible when the real sub is missing. Keep them tuned to the same notes and balanced so the mid layer fills in on small speakers while the sub does the heavy lifting on big ones.
Sidechain the sub to the kick so the two do not fight. The kick and the sub both live in the deep low end, so when they land hard on the same instant they pile up and the bottom turns thick and undefined. Ducking the sub a little each time the kick hits gives the kick a clear moment on its own and lets the sub fill the space around it, so the two read as one solid low end rather than two competing ones.
Sidechain compression turns the sub down briefly whenever the kick plays, then lets it return. Set the dip so it is quick and mostly recovers before the next beat. A small amount is often enough to stop the two masking each other; a larger amount becomes the audible pumping used in a lot of dance music, which is a style choice rather than a fix. If sidechaining is new to you, the what is sidechain compression guide walks through how it works.
Sidechaining is not the only answer. You can also arrange the parts so the sub and the kick simply do not land hard at the same time, placing sub notes in the gaps between kicks. Many solid low ends use both ideas at once: the parts are written to interlock, and a touch of sidechain cleans up whatever overlap is left. What tends not to work is a loud kick and a loud sub hitting the same instant at full level and hoping the bottom stays clear.
Check the sub on more than one system, because no single speaker tells the whole story. On headphones or a big monitor, confirm the weight is there and the note is in tune. On a phone or a laptop, confirm you can still follow the pitch of the line, which is the layer on top doing its job. Then solo the kick and the sub together: if they feel like one steady low sound rather than two fighting ones, the level and the sidechain are set right.
Everything above is about the sub sound: the waveform, the width, the tuning, the level, the layering, the sidechain. That is the half you have just built. The other half is the actual line, the notes and the rhythm you play through it, and it is a separate job you do not have to do by hand.
REHEAT is a writing tool. It generates the bassline you play through your sub patch, so once you have a sub you like you do not also have to labour over the notes. Pick a groove and it writes a line that follows your chords, and you either drag that line out as MIDI or play it live through your sub with the REHEAT MIDI DRIVER, locked to your kick. It runs as an Audio Unit, a VST3 and an AAX.
That split is the point of this page. The sub you build here is the sound; REHEAT supplies the notes to play through it, and the two stay separate, so you can change one without redoing the other.
Free to hear in the browser, no signup. Everything above still works by hand on any synth or bass instrument, which is rather the point of writing it down.
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