pysidstation

Read and write Elektron SidStation patch (.syx) SysEx files in pure Python — no dependencies.

The SidStation is a synthesizer built around the MOS 6581/8580 "SID" chip from the Commodore 64. Its patches are exchanged as MIDI System Exclusive dumps. pysidstation parses those dumps into editable Patch objects and writes them back byte-for-byte.

The complete, corrected file format is documented in docs/FORMAT.md.

Install

pip install pysidstation

Requires Python 3.10+.

Quick start

import sidstation

bank = sidstation.read("SidStation_Presets_r1.syx")

print(len(bank), "patches")          # 90 patches
for patch in bank:
    print(patch.name)                # Anpanman, Krutong, Floating-7, ...

# Edit a patch
lead = bank[0]
lead.name = "My Lead"
lead.poly = True
lead.filter_cutoff = 90
lead.oscillators[0].waveform = sidstation.Waveform.SAW
lead.oscillators[0].ring_mod = True
lead.lfos[0].lfo_type = sidstation.LfoType.RAMP

bank.write("edited.syx")

An unmodified file round-trips exactly:

data = open("SidStation_Presets_r1.syx", "rb").read()
assert sidstation.loads(data).to_bytes() == data

Building a bank from scratch

from sidstation import Bank, Patch, Waveform

p = Patch(name="Init")
p.osc1_enabled = True
p.oscillators[0].waveform = Waveform.PULSE
p.oscillators[0].attack = 2
p.oscillators[0].sustain = 12

bank = Bank.from_patches([p])   # prepends the all-clear message by default
bank.write("init.syx")

What you can read and write

Each Patch exposes the full parameter set as plain attributes that read and write the underlying patch bytes directly:

• Name — patch.name (and patch.name_bytes for the raw 10 bytes)
• Mode — osc1_enabled, osc2_enabled, osc3_enabled, poly, legato, filter_wrap, filter_env_invert
• Filter — filter_routing, filter_osc1/2/3, resonance, filter_type, filter_lfo, filter_cutoff, filter_env_attack/decay/sustain/release, filter_env_depth, filter_lfo_depth, filter_lfo_wheel_depth
• Per-patch sync — sync_speed, sync_hcut
• Oscillators — patch.oscillators[0..2] with waveform, ring_mod, sync, test, sync_pwm, gate, track, arp_speed, transpose, detune, pitchbend_range, attack, decay, sustain, release, delay, pwm_start, pwm_add, pwm_lfo, pwm_lfo_depth, portamento, vibrato_lfo, vibrato_depth, vibrato_wheel_depth, table_speed, plus decode helpers transpose_semitones, detune_value, detune_cents
• LFOs — patch.lfos[0..3] with lfo_type, ctrl_source, ctrl_dest, sync, invert, above_zero, sync_note_off, speed, sample_hold, depth, add_lfo, lace, lace_with, add_depth, ctrl_value, fade_in
• Direct controllers — patch.direct_controllers[0..3] with value, limit_down, limit_up
• Tables — patch.tables (three Tables of TableSteps) and patch.replace_tables(...)

Need the raw bytes? patch.data is the mutable, decoded bytearray that backs every attribute above, indexed exactly as in docs/FORMAT.md.

Command line

sidstation info  SidStation_Presets_r1.syx   # summary table
sidstation names SidStation_Presets_r1.syx   # one name per line
sidstation show  SidStation_Presets_r1.syx 0 # detail for patch 0

(Equivalently python -m sidstation ....)

A couple of things the manual gets wrong

pysidstation is built from the owner's manual and verified against a real bank. A few corrections matter in practice:

• Every stored parameter byte is nibble-swapped relative to the synth's working value. The library undoes this on load (and re-applies on save), so patch.data and every attribute hold the synth's true values while files still round-trip byte-for-byte. This single fact is why the manual's waveform, LFO-type and detune layouts looked off — once un-swapped they line up. (e.g. the waveform is really in the OSC_WAVE high nibble, SID-control style.)
• LFO type 5 is "Flat", not 7, and detune spans ≈ ±1 semitone, not ±½ — both corrections to the manual's tables.
• The size field in each patch header is unreliable (54 of 90 patches in the reference bank disagree with it). The library parses by message boundary and preserves the stored value so files still round-trip exactly.

All are explained in docs/FORMAT.md.

Development

pip install -e ".[dev,lint]"
pytest
ruff check .
ruff format --check .

The test suite uses Elektron's factory preset bank as a fixture. That file is Elektron's copyrighted content and is not committed here — tests/conftest.py downloads it on demand from Elektron's official SidStation Sound Pack archive, verifies its SHA-256, and caches it locally. To run offline, point SIDSTATION_PRESETS at a local copy; if it can't be obtained, the dependent tests are skipped.

All tests run in CI (GitHub Actions) across Python 3.10–3.13, and the distribution is built and checked there too. The lint job uses the pinned ruff from the lint extra, which Dependabot keeps current.

License

Apache-2.0. See LICENSE.

SidStation and Elektron are trademarks of Elektron Music Machines. This is an independent, unofficial library and is not affiliated with or endorsed by Elektron.