Machine
AC 303: a free acid bass synth with accent and slide
AC 303 is the BASS machine in EASY RAVE, a free bass synthesizer in your browser inspired by the TB-303 acid sound. It has a resonant filter with envelope and accent, a piano roll with ACCENT and SLIDE lanes, a RANDOM key that writes acid lines in key, SING to turn your voice into a bassline, an arpeggiator and a SUB knob for low end on small speakers.
What is AC 303?
AC 303 is the bass synthesizer in the EASY RAVE rack, labelled BASS. It is an original synth inspired by the Roland TB-303, the small bass machine from 1981 whose squelchy, resonant sound became acid house.
It plays one note at a time, like the original idea, and every note can be accented or slide into the next. That combination, plus a filter you sweep by hand, is what makes a bassline sound acid.
What do the knobs do?
| Knob | What it does |
|---|---|
| Wave screen | Click to change the oscillator: SAW (the classic acid buzz), SQU (hollower), TRI and SIN (softest, for deep subby lines) |
| CUT OFF FREQ | How open and bright the bass is. The main knob to perform with |
| RESONANCE | The squelch: a whistling peak at the cutoff |
| SUB | A clean sub bass under every note, so the line has weight on small speakers |
| ENV MOD | How far each note sweeps the filter open |
| DECAY | How long each note rings and sweeps |
| ACCENT | How much harder the accented notes hit |
| DRIVE | Overdrive grit, without making the bass louder |
| TUNING | Moves the whole bass higher or lower |
Hold Z anywhere and turn the mouse wheel to sweep the cutoff while you watch the rest of the rack. Filter cutoff and resonance explains these knobs by ear.
How do you write a bassline on AC 303?
AC 303 has a piano roll: rows are notes, columns are the 16 steps of a bar. It only shows the notes of the key you chose with ROOT and SCALE at the top, so every note you click fits the song.
- Click a cell to place a note, and drag its right edge to make it longer.
- ACCENT lane: click A under a step to accent that note.
- SLIDE lane: click S under a step to glide into the next note. If you cannot see it, drag the handle under the roll to make it taller.
- OCT − / OCT + move everything an octave down or up, and ♭ / ♯ move the notes one step along the scale.
A classic acid line in C minor
| 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| NOTE | C2 | C2 | C3 | C2 | C2 | C3 | C2 | C2 | C2 | C3 | C2 | C2 | ||||
| ACCENT | A | A | A | A | A | |||||||||||
| SLIDE | S | S | S |
Acid bassline patterns has 5 more lines like this one.
What are RANDOM, SING and STEP?
These 3 keys on the tag line give you faster ways to get notes in:
- RANDOM writes a new acid line into the bar you are viewing, in key, with accents and slides. Press it until something grabs you, then edit it.
- SING listens to your microphone while you hum or sing, and writes the line as notes, in key and in the bass range. See hum a bassline.
- STEP records one note per step from the number keys while the song is stopped. The arrow keys move the cursor, and → on its own leaves a rest.
You can also press LIVE and play the bass on the number keys, or press ● REC to record a take with a one bar count-in, quantised to 16ths.
What does the arpeggiator do?
The ARP panel turns held notes into a pattern. Switch it on, press LIVE, and hold 2 or more number keys: AC 303 plays them one after another in time with the song. Choose ARP: UP, DOWN, UP-DOWN or RANDOM, a speed of 1/16, 1/8 or 1/8T (triplets), and 1 or 2 octaves.
Which presets come with it?
PRESETS has 5 basslines: Classic acid, Rolling 16ths, Octave bounce, Deep house and Offbeat sub. They follow your key and scale.
Frequently asked questions
Is AC 303 the same as a TB-303?
No. AC 303 is an original bass synth built for EASY RAVE and inspired by the TB-303 sound: a resonant filter, accents and slides. It is not a recreation of the Roland circuit, and EASY RAVE has no connection with Roland.
Can I make acid house with AC 303?
Yes. Program a line with accents and slides, turn RESONANCE past halfway, set ENV MOD and DECAY, and sweep CUT OFF FREQ while a house beat plays. How to make acid house goes through it step by step.
Is there a free online 303?
EASY RAVE's AC 303 is a free bass synth in the 303 style that runs in your browser, with the step sequencer, accents, slides and resonant filter that acid lines need. No download or account is required.