GeCo-Tools

§ 01

GeCo-Tools — The Hub

GeCo-Tools is the central launcher of the suite. It opens as a single page with a dark, glass-effect menu panel positioned over a full-screen background image. From here the user reaches each of the five specialized tools with a single click, and can also access the manual and video tutorials through the collapsible Guides & Tutorials dropdown.

All five tools share the same visual language (blue header bar, white panel, score area) and the same common features: in-browser audio playback with Piano or Sax B♭ soundfonts, adjustable BPM (60–240), optional metronome with three click sounds, MIDI export/import, score rendering via OpenSheetMusicDisplay, and an animated pitch-class circle that lights up notes in real time during playback.

§ 02

Compose by Interval Matrix — GeCo-Tool

GeCo-Tool is the core compositional engine. The user defines a chain of intervals (in semitones, positive = ascending, negative = descending) and chooses a sequence type that determines how many intervals form one repeating block. The engine applies the block cyclically from a chosen starting note and stops automatically the first time the pitch returns exactly to the starting pitch class — guaranteeing a self-closing, geometrically coherent loop. Two calculated fields, Jump (algebraic sum of intervals) and Length (total number of notes before closure), update live as parameters are edited.

Sequence Types

• Binary — one interval + one leap per cycle block (2 values).
• Ternary — three consecutive intervals per block (3 values).
• Quaternary — two interval/leap pairs per block (4 values).
• Senary — three interval/leap pairs per block (6 values).
• Multidimensional — freely set N intervals (1–12) per block.

Rhythm Modes

• Constant — all notes share the same duration (whole → sixteenth).
• Sequence-constrained — durations change at cycle boundaries.
• Length-constrained — durations change every N notes, N ∈ {2, 3, 5, 6}.
• Free — each note gets an independent random duration.

Pitch-Class Transformations

• T (Transpose) — shifts all pitches by a chosen number of semitones (−12 to +12).
• I (Inversion) — mirrors every interval around the first note.
• R (Retrograde) — reverses the pitch sequence.
• RI (Retrograde-Inversion) — inversion followed by retrograde.

Rhythmic Transformations

• S+ — cyclically advances the duration pattern by two steps.
• S− — cyclically retards the duration pattern by two steps.
• I — rhythmic inversion: long and short durations swap rank.
• R — rhythmic retrograde: duration sequence reversed, pitches unchanged.

Additional Options

• Harmony — adds a bass-clef accompaniment in three styles: Classic (paired notes), On the beat, Off the beat.
• Octaves — constrains the melody to approx. 1 or 2 octaves of range.
• Bass Clef — transposes output two octaves down and notates in bass clef.
• Swing — delays off-beat eighth notes; intensity set by a slider (50 % = straight, 67 % = full 2:1 swing).
• Key Signature — sets the displayed key signature (does not alter pitches or MIDI).
• MIDI Import/Export — saves or reloads sequences as .mid + .txt parameter files.
• Docs panel — in-app access to HTML documents and PDF resources (interval tables, scale presets, theory references).

§ 03

K-Random — Random Generation and Practice

K-Random generates short melodic sequences of exactly K notes (2–12) by sampling randomly from pitch-class sets with optional repetition control. It is designed both as a compositional tool for aleatoric fragments and as a sight-reading / ear-training aid.

Generation Parameters

• Start Note — the pitch class that begins the sequence (C–B); octave assigned automatically.
• K (number of notes) — length of the sequence (2–12). Cannot exceed 12 if Repeated is off.
• Repeated — when unchecked, each pitch class appears at most once (chromatic subset); when checked, repetitions are allowed.

Rhythm

• Constant — uniform note length chosen from the selector.
• Length-constrained — durations change every N notes, N ∈ {2, 3, 5, 6}.
• Free — each note receives an independent random duration.
• Allow Triplets — enables triplet groupings with a probability slider (0–100 %).

Pitch-Class and Rhythmic Transformations

The same four pitch-class operations (T, I, R, RI) and four rhythmic operations (S+, S−, I, R) available in GeCo-Tool can be applied to any generated sequence after the fact.

Pitch-Class Circle

An animated clock-face circle (top left) lights active notes in gold during playback and traces melodic arcs between them; the first and last arcs are highlighted in white. A row of coloured interval boxes below the controls shows the signed semitone distance between each consecutive pair of notes.

§ 04

Twelve-Tone Studies

The Twelve-Tone Calculator generates melodic sequences from a user-defined vector of 12 intervals (i1–i12, in semitones), starting from a chosen pitch class. It is oriented toward dodecaphonic and serial composition in the tradition of the Second Viennese School, but works equally well for any 12-note interval chain.

Generation Parameters

• Start Note — the pitch class where the row begins (C–B).
• Interval Vector i1–i12 — twelve signed integers defining the twelve successive melodic steps. Default is all 1s (chromatic ascent).
• Limit to 12 notes — truncates the generated output to exactly 12 notes.

Rhythm, Harmony, Transformations

All rhythm modes (constant, sequence-constrained, length-constrained, free), the Harmony bass-clef accompaniment option, and both pitch-class and rhythmic transformation sets (T, I, R, RI / S+, S−, I, R) are identical to those in GeCo-Tool.

MIDI Export

Download saves two files simultaneously: twelve_tone.mid (the sequence) and twelve_tone.txt (all parameter settings), which can be reloaded together via Import MIDI to restore the exact state.

§ 05

Sequence Join — GeCo-Join

GeCo-Join is a MIDI file joiner. It lets you load multiple .mid files onto a Forth-style last-in / first-out stack, concatenates them in stack order into a single continuous sequence, renders the result as standard notation, and allows playback or export as a new MIDI file.

Importing Files

• Import MIDI — opens a file picker accepting one or more .mid files; all selected files are pushed onto the stack and immediately joined.
• Append MIDI — adds a single file to the top of the existing stack and re-joins automatically.

Stack Operations

• Pop — removes the top (last) file from the stack.
• Rotate — moves the top file to the bottom, cycling play order: [A, B, C] → [C, A, B].
• Swap — exchanges the last two files: [A, B, C] → [A, C, B].
• Reset — clears the stack and reloads the page.

Every stack operation immediately re-joins the remaining files and re-renders the score. The Key Signature selector adjusts the displayed notation without altering audio or MIDI content.

§ 06

Practice

Practice is a focused playback and notation tool designed for instrument practice and ear training. Instead of generating sequences from scratch, it imports a preset — a .txt file in GeCo syntax containing a list of intervals — and immediately renders the corresponding melodic sequence as notation, ready for playback.

Generation Parameters

• Start Note — pitch class on which the imported sequence begins (C–B).
• Note Length — uniform duration for every note: Whole, Half, Quarter, Eighth, or Sixteenth.

Preset Import

• Import Preset — loads a .txt interval preset (e.g. a scale or arpeggio pattern exported from GeCo-Tool).
• GeCo-Tool .txt export files are fully compatible, making it easy to practise any generated pattern at a chosen tempo and starting note.

Transformations and Export

The full set of pitch-class transformations (T, I, R, RI) is available after import, allowing the user to practise a scale pattern in inversion or retrograde without editing the original file. Download exports the current sequence as a .mid file.

§ 07

Additional documentation and utility files

Additional resources are available through the Docs section of "Compose by Interval Matrix".