What is acid house?
Acid house is a branch of house music built around repetitive electronic grooves and a resonant, liquid bass sound associated with the 303 sequencing language. The most important idea is transformation: a short pattern repeats while filter cutoff, resonance, envelope movement, accent and slide continually change how that pattern feels.
You do not need a dense melody. Many convincing acid lines use only a few pitch classes. The groove comes from where notes are placed, where silence appears and how selected notes are emphasized or connected.
What makes a 303 bassline sound like acid?
1. Rhythm before melody
Start by deciding which of the sixteen steps actually contain energy. Four-on-the-floor drums can be very straight while the bass line sits between the kicks, skips a beat, answers the backbeat or leaves a deliberate hole before a strong accent.
2. A small pitch vocabulary
Choose a root note and a handful of nearby notes. Repetition is useful. A repeated note with different octave, accent or slide behavior can sound more alive than a constantly changing melody.
3. Accent
Accent should create pressure points. On a 303-style line it is not merely “louder”; it changes the perceived attack and filter energy. Use it to make selected steps bark through the groove rather than marking every step.
4. Slide
Slide connects one pitch to the next without the line feeling like two completely separate note events. The best slides are intentional: use them when the destination pitch creates tension or release. Sliding every note usually removes contrast.
5. Octave movement
An octave jump can make a one-note motif suddenly feel like a new phrase. Alternating low and high versions of the same note is one of the fastest ways to create the bouncing robotic character associated with acid sequencing.
What BPM is acid house?
Classic acid house commonly sits around the high teens through the low 130s BPM. Harder acid techno and rave styles can move considerably faster. Instead of treating one number as “correct”, match tempo to the density of the line: busier patterns often need more space, while sparse patterns can tolerate more speed.
303box uses several acid-oriented generation profiles rather than forcing every pattern to the same BPM. The goal is to keep the bass and rhythm musically related instead of producing two unrelated random grids.
How to get the squelch
The recognizable acid voice comes from the interaction of waveform, low-pass filtering, resonance and envelope movement. Start with either saw or square. Raise resonance until the filter becomes a strong part of the timbre, keep cutoff low enough to leave room for movement, then increase envelope modulation so each note pushes the filter open.
Decay controls how long that filter movement hangs around. Short settings feel tight and rubbery; longer settings smear the motion across the groove. After the basic line works, delay can add rhythmic space and distortion can add aggression. Effects should support the pattern, not replace it.
A practical five-minute acid workflow
- Choose a tempo and start with a simple kick-and-hat rhythm.
- Place six to ten bass triggers across the sixteen steps and leave real rests.
- Use three to five notes from a dark or ambiguous pitch set.
- Add two or three accents on musically important steps.
- Add one or two slides into meaningful target notes.
- Introduce one or two octave jumps.
- Loop the pattern and perform cutoff, resonance, env mod and decay.
- Only after the dry line works, add delay or distortion.
303 and rhythm: why the relationship matters
Acid house is a conversation between the bass line and the rhythm section. A kick on every quarter note gives a stable floor, while closed and open hats establish subdivision and forward motion. Claps or snares can mark the backbeat, and toms can create transitions or fills.
303box keeps rhythm and bass in the same tempo domain so you can hear this relationship immediately. You can generate them together for a coherent starting point or regenerate only the rhythm while preserving your existing 303 tempo.
Browser MIDI and hardware workflow
The browser can be more than a demo environment. When Web MIDI is available and a real MIDI output is connected, 303box can route note information to external hardware. That makes the site useful as a sketchpad before a session, a pattern reference during a session or a browser-based front end when you want to generate ideas quickly.
If you prefer a completely hardware workflow, export the visible pattern as an image and program the notes, octave moves, accents and slides manually.
Acid house FAQ
Do I need a real 303 to make acid?
No. The musical language is defined by sequencing and synthesis behavior. Hardware, software and browser instruments can all explore the same core ideas.
Is slide the same as simply changing pitch?
No. A normal note change starts a separate note event. A slide keeps continuity and moves pitch through the transition, which changes the phrasing dramatically.
Should resonance always be maximum?
No. High resonance is iconic, but contrast matters. Moderate resonance with moving cutoff can be more usable in a mix, especially once distortion is added.
Can beginners use 303box?
Yes. Generate gives you a musically structured starting point, while every step remains editable so you can learn by changing one decision at a time.