Melodic Techno Bass in Serum 2: How to Build a Rolling Bassline

A good melodic techno bass in Serum 2 does two jobs at once. It keeps the low end steady under the kick, and it rolls between the kicks with enough tone that you can follow the notes on a laptop speaker. Here's how I build a rolling bass in Xfer Serum 2 from an empty patch, which settings actually matter, and how I get it to sit with the kick in Logic Pro.

What a melodic techno bass in Serum 2 has to do

Think of the bass as two layers inside one patch. The bottom layer is the sub: mono, steady, the same on every note, with no effects on it. The top layer is the part you actually hear as "the bass": a filtered saw with a short envelope that gives each sixteenth a little bite. Serum 2 makes this split easy, because you can send each oscillator to a different place. Once you build the patch around that idea, the mixing gets much simpler.

For melodic techno around 122 to 128 BPM, I keep the root notes of the bassline roughly between E1 (about 41 Hz) and A1 (55 Hz). Lower than that and the sub turns into pressure you feel more than hear. Higher and it starts to crowd the chords.

Step 1: write the MIDI before you touch the synth

The pattern decides more about the sound than any knob. A classic rolling bass leaves the kick alone and plays the three sixteenths after it, so the bass fills the gaps instead of fighting the transient. In a bar of 4/4 that means notes on the second, third and fourth sixteenth of every beat.

• Note length: keep notes short, a bit under a sixteenth. At 126 BPM a sixteenth lasts about 119 milliseconds.
• Velocity: give the first note after each kick a higher velocity than the other two. We'll use that later to open the filter more on accents.
• Notes: stay on the root for most of the bar and move only on the last beat or two. Melodic techno basslines feel hypnotic because they change slowly.

Loop it against your kick before you design anything. If the groove doesn't work with a plain sine, it won't work with a great patch either.

Step 2: oscillators and the sub

Serum 2 has three main oscillators, plus the sub and noise oscillators. For this bass I use oscillator A, oscillator B and the sub. Everything else stays off.

Oscillator A: the body

• Wavetable: a plain saw.
• Unison: 1 voice. The body of the bass stays mono and centred.
• Phase: set RAND to 0, so every note starts at the same point of the wave. With random phase, each sixteenth hits a little differently, which sounds nice on pads and sloppy on a bass.
• Routing: Filter 1. This is the default for oscillator A anyway.

Oscillator B: a bit of width on top

• Wavetable: the same saw, one octave up.
• Unison: 3 or 4 voices with a low Detune. This is the only stereo part of the patch, and because it sits an octave up, the width lives above the sub where it can't cause phase trouble.
• Level: well below oscillator A. You should notice it when you mute it, not when it plays.
• Routing: change it to Filter 1 as well, so both saws share one filter and move together. By default the other oscillators go to the main output and skip the filter.

The sub: clean and direct

Switch on the sub oscillator, pick the sine shape and tune it so it lands one octave below oscillator A. Now open its routing and choose Direct. The Serum 2 manual describes Direct as bypassing the filters and the effects, so the sub plays clean next to the main output. That's exactly what you want: you can distort and filter the top layer as much as you like and the low end stays round, mono and consistent.

Step 3: the amp envelope

Envelope 1 controls the volume in Serum 2. For a rolling bass I start here:

• Attack: 0 to 2 ms. Go up a millisecond or two if you hear clicks.
• Hold: 0.
• Decay: around 150 to 250 ms.
• Sustain: low, around 20 to 35 percent.
• Release: short, 30 to 60 ms. A long release makes notes overlap and the groove goes soft.

Because the notes are short, you mostly hear the attack and decay. That's the point: the bass speaks, then gets out of the way before the next kick.

Step 4: filter and envelope 2, where the bass gets its bite

Set Filter 1 to MG Low 24. It's a warm, analog style lowpass and it handles a saw bass well. Then:

• Cutoff: low, around 200 to 400 Hz. Solo, the bass should sound dark and a bit muffled.
• Resonance: 10 to 20 percent. A little gives the envelope sweep a vowel like quality. More than that and the low notes start to boom.
• Drive: a small amount for some weight. Serum 2 added a clean mode for the filter Drive, so you can choose whether it colours the sound or just adds level.

Now drag envelope 2 onto the cutoff and set it up as a pluck: attack 0, decay around 80 to 150 ms, sustain 0, release short. The modulation amount decides how far the filter opens on each note. Start with a moderate amount and listen in the track, not in solo.

Two more routings in the mod matrix make a big difference:

• Velocity to cutoff: a small amount. Remember those louder notes after each kick? They now open the filter a little more, and the line gets an accent pattern without any automation.
• A macro for the whole filter: put cutoff and the envelope 2 amount on one macro. One knob now takes the bass from dark and round to open and biting, which is the move you'll automate in every build.

If you want to compare this approach with an analog emulation, I built a similar bass in u-he Diva for melodic techno. The thinking is the same, only the filter character changes.

Step 5: voicing, legato and slides

Set the voicing to mono. A bass should never play two notes on top of each other, and mono stops tails from stacking up in the low end.

Legato and portamento are for slides. With legato on, notes that overlap don't restart the envelopes, and with a short portamento time they glide into each other. I keep the notes separate in most of the pattern, so every sixteenth retriggers, and only overlap the one or two notes where I want a slide. Serum 2 also has an Invert Legato option per envelope that forces an envelope to retrigger even with legato on. That's useful when you want the pitch to glide but the filter to pluck on every note.

Step 6: movement over seven minutes

The pattern can stay the same for a long time in melodic techno, so the tone has to move instead. My usual setup:

• A slow LFO on cutoff: synced to 4 or 8 bars, small depth. The bass breathes without you drawing anything.
• Automate the macro, not the knobs: close it slightly in the breakdown and open it over the last 16 bars of the build.
• Oscillator B level on a second macro: bring the octave layer in for the drop and pull it back in quieter sections.

I wrote more about this kind of motion in how rhythmic modulation shapes energy in techno.

Step 7: effects inside Serum 2

Since the sub goes Direct, everything in the effects rack only touches the top layer. That gives you freedom.

• Distortion: the new Overdrive mode, with a low mix. It adds harmonics that let the bass read on small speakers.
• Splitter L/H: Serum 2's splitter effects let you build separate chains per frequency band. Put the distortion on the high band only, and the low mids of the saw stay solid while the upper harmonics get gritty.
• EQ: a gentle dip around 250 to 350 Hz if the bass feels boxy next to the kick.
• No reverb, no chorus. If you want space, use a short delay on a send in the DAW and filter the low end out of it.

Step 8: kick and bass in Logic Pro

Solo, this bass will sound fine. The real test is the kick.

• Tune the key to the kick. Look at your kick on Channel EQ's analyzer and find where its low end peaks. If the bass root sits right on top of it, either retune the kick or move the track to a key where the root lands a bit higher or lower.
• Sidechain. Logic's Compressor on the bass with the kick as side chain input, fast attack and a release short enough that the bass is back by the first rolling sixteenth. A rolling pattern already avoids the kick, so you need less gain reduction than you'd expect.
• Low cut. A gentle high pass around 30 Hz removes rumble you can't hear but your limiter can.
• Check mono. Flip the master to mono. Only oscillator B should change, and only slightly. If the bass drops a lot, lower the unison Detune or the level of oscillator B.

If you also run wide leads above this, my post on making melodic techno leads wide without killing their power covers the same mono checks for the top of the mix.

Common mistakes with Serum 2 basses

• Unison on the main oscillator. It sounds huge solo, then the low end goes hollow on a mono club system. Keep width on the octave layer only.
• Running the sub through the effects. One distortion or chorus on the sub and the low end changes with every note. Route it Direct.
• Filter envelope longer than the note. If the decay is much longer than a sixteenth, every note sounds the same and the groove flattens.
• Too much resonance. It whistles on the high notes and booms on the low ones. Use Drive or Overdrive for bite instead.

Questions producers ask

Which filter should I use for melodic techno bass in Serum 2?

MG Low 24 is my starting point for a warm, round bass. MG Low 12 is a little brighter and lets more harmonics through, which helps when the bass has to cut through a dense mix.

Should a Serum 2 bass be mono?

The low end should be. Keep oscillator A and the sub mono and centred, and put any width on a quiet octave layer above them.

How do I stop my Serum 2 bass from clicking?

Set the oscillator phase randomization to 0, give the amp envelope an attack of 1 or 2 ms and make sure the release isn't so short that notes cut off mid wave.

Do I need legato and portamento for a rolling bass?

Not for the main pattern. Use mono with separate notes so every sixteenth retriggers, and overlap notes only where you want a slide.

Build this patch once, save it as your own bass starting point, and the next track starts with a low end you already trust. If you'd rather pull finished sounds apart first, grab the free After Dark Serum 2 presets, and when you want the full set of basses, leads and stabs, have a listen to After Dark.