Crackle Tracker

A TIC-80 tracker for tiny intros, targeting especially the 512b size category.

Introduction

The tracker supports 4 channels. Instrument settings are per channel. The sound of each channel is controlled by the values in the "Instrs" table.

Each channel has its order list which tells the general structure of the song: which patterns appear in which order. Note that a pattern usually is repeated several times before the order list advances.

The patterns are edited by semitone values, in base 36 (0-9A-Z). "-" denotes no note.

Each note has a linearly decaying envelope (no attack, no sustain) and this cannot be changed.

Importantly, the note duration of different channels do not have to be the same, so the pattern row advances at different rates for each channel, controlled by the NoteDur parameter. For example, even if all channels are playing the exact same pattern, if one channel is playing whole notes, one channel is playing half notes and one channel quarter notes, the phrase loops when the channel that was playing whole notes loops.

Nevertheless, the order list advances at the same time for all the channels.

There is one extra channel, the "transpose channel". This channels values are added to the pitch of all channels, to change the current chord of the song. If your patterns only have notes from the power chords (0, 7, C (12)...), you can use many different values here and still the overall song stays in (some) key. If your patterns have notes only from minor triads or major triads, at least values 0-5-7 (I-IV-V or i-iv-v, respectively) stay in key. If you're fine with jazz, anything works.

NOTE: "-" is actually 255, so the patterns the transpose channel is playing should not contain "-"; use 0 instead.

The song data is kept in the persistent memory (pmem), so you can quit and restart TIC-80 and the song should stay in memory.

Instrument settings

• Wave: 0 = square, 1 = triangle, 2 = saw, 3 = noise. Triangle and saw have terrible high frequency whine, so most of the time, only square and noise are really useful.
• Octave: 12*octave is added to the note number.
• Interval: Interval (within the scale) that is added to the note number. e.g. intervals 0, 2, 4 harmonize the major triads.
• NoteDur: Controls how fast the pattern row advances or the duration of each pattern row. 1 = whole note, 2 = half note, 4 = quarter note, 8 = eight note, G (16) = sixteenth note
• Fill: Controls if following pattern(s) are played instead of repeating the same pattern every time. To be documented how it actually works...
• Mute: Temporarily mute channel.
• Slide: How quickly the pitch of the channel drops. 0 = no drop, 8 = typical for a kick.
• Arpeggio: When using diatonic scale, it arpeggiate with this many thirds on top of the bass note, so 1 = arpeggiate between root and third of the chord, 2 = arpeggiate between root, third and fifth of the chord... etc.

Song settings

• Ordlen: Length of the order list.
• PatReps: How slowly the order list is advanced.
• PatLen: What is the length of each pattern, in rows.
• Tempo: Controls the tempo of the song. Actually, the envelope of each note it calculated with %(16-tempo), so increasing the tempo also decreases the master volume.
• Key: Added to all note values of the song, controlling essentially the key of the song.
• ChdDur: How quickly the pattern rows of the chord channel advance.
• Scale: What scale to use. Most usefuls are: 0 = chromatic, 5 = pentatonic, and 7 = diatonic.
• Mode: What mode of the scale to use. In particular, when using the diatonic scale, 1 = ionian, 2 = dorian... etc.
• Invers: Works as intended only when using diatonic scales. Controls how much chords are inverted. 0 = off, 2 = all chords are inverted so that bass changes as little as possible.

Exporting

Since TIC-80 has no way to access the file system, the only practical way to export data from TIC-80 is by abusing the trace command. When you click export, a fully functional TIC-80 LUA script that includes the player and the song data is outputted to the console. You can then copy-paste this to another file & start hand-optimizing unused player features away.

The exported player stores the envelopes data array: d[0], d[-1], d[-2] and d[-3] contain the envelopes of the channels 0-3, respectively, so you can make your visuals flash to the music.

Saving & Loading

Saving works like exporting: when you save the song, the tracker prints code to the console. When the code is ran, the song just saved is loaded to the persistent memory. For example, if you copy-pasted the code to a file called saved-song.lua, in order to load the song:

1. load saved-song.lua
2. run
3. load crackle-tracker.lua
4. run

The saving mechanism abuses -- saveid: script tag to make multiple .lua files access the same persistent memory.

Prods using Crackle Tracker

cracklebass by brainlez Coders! - Song included in the examples folder.

Pulsating Magic Orb by brainlez Coders! - Song included in the examples folder.

stroboscope by brainlez Coders! - Song included in the examples folder.

Credits

Veikko Sariola aka pestis/brainlez Coders!

License: MIT