🕹️ Commodore 64 / SID Support

MidiEditor AI opens Commodore 64 .sid tunes like any other file: the three SID voices become editable MIDI tracks, and you can hear the result two ways - as the converted MIDI dressed in real C64 timbres, or as the original SID played through a cycle-accurate emulator. A single C64 toolbar button drives whichever of those you choose in Settings.

C64 mode in action - Commando.sid played back in Emulation mode (click to play with sound).

Opening a SID tune

Use File → Open (or drag a file onto the window) and pick a .sid file. MidiEditor AI plays the tune internally, watches what the SID chip does frame by frame, and reconstructs it as a standard MIDI file you can edit:

One track per SID voice (the C64 has three), so each melodic line, bass, and lead lands on its own track and MIDI channel.
A dedicated SID Percussion track for the noise-based drum hits a voice plays between notes.
Note pitches, lengths, velocities, and fast arpeggios are recovered from the chip's gate and envelope behaviour.

A SID tune imported into MidiEditor AI, showing three voice tracks plus a SID Percussion track in the piano roll.

An imported SID tune: three voices plus a percussion track, ready to edit and play.

SID tunes loop forever - so how long is the import? A SID has no built-in end; it just keeps playing. MidiEditor AI looks for the point where the music starts repeating and trims the import to the intro plus one loop. When it can't find a clean loop it falls back to a fixed length (240 seconds by default) - you can change that fallback under Settings, and long one-shot tunes will ask you to confirm a length on import.

Hearing it - the C64 button

Imported SID tracks use General-MIDI instruments by default, which won't sound like a C64. The C64 toolbar button switches on the authentic C64 sound. It has two jobs depending on the engine you pick (see Choosing the engine) - but it's always the same one button, and it lights up (the Commodore logo glows) when it's active.

The C64 button toggling off ↔ active (the logo lights up when on).

SoundFont mode - the converted MIDI, C64 timbres

In SoundFont mode the C64 button plays the converted MIDI through a Commodore 64 SoundFont, remapping the imported instruments onto the SID's classic waveform voices - pulse, sawtooth, triangle, and noise. The result is the familiar C64 character, while you keep a normal, editable MIDI file.

The C64 SoundFont downloads itself on first use The first time you turn on SoundFont mode without a Commodore 64 .sf2 installed, MidiEditor AI offers to download it automatically (exactly like FFXIV SoundFont Mode) - just confirm the prompt. It also switches the MIDI output to the built-in FluidSynth so the C64 timbres play. You can still install one manually via the SoundFont manager or by dropping a .sf2 into the app's soundfonts folder. Turning the mode off restores your previous (General MIDI) selection automatically.

SoundFont credit: Commodore 64 SoundFont by jubbyo, from musical-artifacts.com/artifacts/8014 (CC BY-NC). Used for non-commercial playback; not bundled with the app - it is downloaded on demand.

Emulation mode - the original SID, authentic

In Emulation mode the C64 button plays the original .sid file through the cycle-accurate libsidplayfp engine - the same engine dedicated SID players use - for true-to-hardware chip audio. Here the button arms the mode (it glows when armed); the actual playback is driven by the normal transport, so it behaves like real playback:

Play starts the original tune from the cursor position.
Stop and Pause work as usual (Pause parks the cursor where you stopped).
Seek by clicking to move the cursor, then Play from there.
The piano-roll cursor follows the audio in real-time sync.
Playback stops at the end of the note roll instead of looping forever.

Because Emulation mode plays the real SID while you still see (and can edit) the converted MIDI, it's perfect for A/B-ing your edits against the original.

💾 Export it too: with Emulation active you can render the authentic SID straight to audio - Export Audio writes the real libsidplayfp sound (WAV / FLAC / OGG / MP3, whole tune, no SoundFont needed) instead of the converted MIDI.

Choosing the engine

The very first time you turn C64 mode on, MidiEditor AI asks once how you want C64 tunes to play - C64 SoundFont or Emulation - and remembers your choice. The C64 SoundFont (~11 MB) is fetched in the background so either engine works instantly later, even if you change your mind.

To switch engines afterwards you don't need to open Settings: a retro SF2 ↔ EMU toggle appears in the toolbar next to the C64 button whenever C64 mode is active. The lit side is the current engine; click to flip. (The C64 button still does the activating - the toggle only chooses which engine it uses.)

The retro SF2 to EMU toolbar toggle, with the active engine side glowing.

The SF2 ↔ EMU engine toggle (shown only while C64 mode is active).

You can also set the engine in Settings → MIDI I/O → Commodore 64 / SID - the toggle, the first-use prompt and the Settings radio all stay in sync.

💡 No .sid loaded? Emulation is locked. Emulation plays the original .sid bytes, so it only works while a .sid is the open file. With any other file - a plain MIDI, or a SID you imported and then saved as .mid - the SF2 ↔ EMU toggle's EMU side is greyed out and locked to SF2, and the Settings radio disables Emulation. SoundFont mode still works on any MIDI, so you can give an ordinary song C64 timbres (a fun chiptune effect) even though there's nothing to emulate. Open a .sid and Emulation unlocks again; your engine preference is remembered the whole time.

Muting voices while it plays

In Emulation mode, muting follows your edits live. Mute a channel or a track (the speaker toggle) and the matching SID voice goes silent immediately - handy for soloing the bass line or dropping the lead while the tune plays. Hiding a track is purely visual and does not mute it, exactly like everywhere else in the editor.

Choosing the engine - Settings

Open Settings → MIDI I/O and find the Commodore 64 / SID section:

Option	What it does
C64 sound	Pick what the C64 toolbar button activates: SoundFont (converted MIDI with C64 timbres) or Emulation (the original `.sid` via libsidplayfp).
Default SID import length	The fallback capture length (5-600 s) used when a tune's loop point can't be detected automatically.

The Commodore 64 / SID settings block.

Switching engines takes effect right away If C64 sound is already on and you switch the engine, the active state moves to the newly chosen engine immediately - you don't have to toggle the C64 button off and on again.

A note on PSID vs. RSID tunes

The SID format comes in two flavours. PSID tunes are played by a fast built-in emulator. RSID tunes install their own player and need full C64 hardware emulation, so they're imported through the libsidplayfp engine for accuracy - you don't have to do anything differently, it's automatic (RSID imports just take a moment longer and show a progress bar). The whole feature runs without any C64 ROM files. A handful of unusual tunes may not import cleanly; when that happens the app tells you rather than producing noise.