User:Contribution/Chanopif Project

Chanopif (short for Channel-Note-Pitch-Fractional pitch) is a proposed file format and specification designed to enable precise microtonal tuning for electronic and software-based musical instruments under the MIDI 2.0 standard. The format uses the .cnpf file extension and leverages the 7.25 pitch attribute (Registered Per-Note Controller #3) defined in MIDI 2.0 to achieve extremely fine pitch resolution—specifically 402,653,184 subdivisions per octave (402,653,184-EDO).

Etymology

The name Chanopif is derived from its four core elements:

Cha-: Channel
-no-: Note
-pi-: Pitch
-f: Fractional pitch

These components underscore the file format’s focus on assigning precise pitch data to specific MIDI channels and note numbers.

Background: MIDI 2.0 Pitch 7.25

In MIDI 2.0, Registered Per-Note Controller #3: Pitch 7.25 provides a high-resolution method for defining pitch beyond standard 12-tone equal temperament (12-EDO). The 32-bit data field for Pitch 7.25 is split into:

7 bits for the integer part (the “traditional” note number in semitones). 25 bits for the fractional part of a semitone.

This gives 2^7 = 128 distinct note values (as in MIDI 1.0), each further divided into 2^25 microsteps, resulting in a total of 402,653,184 equal divisions per octave (12 semitones × 2^25). This extreme resolution allows for microtonal tunings with sub-cent precision. File Format

A Chanopif (.cnpf) file is a plain-text file containing a series of lines. Each line follows the pattern:

decimal_channel hex_note_number hex_pitch7bits.fractionalPitch25bits_base32

Where:

   decimal_channel
       MIDI channel index, ranging from 1 to 256 in MIDI 2.0 (or 1 to 16 in MIDI 1.0).

   hex_note_number
       The MIDI note number expressed in hexadecimal, ranging from 00 to 7F or 8F (depending on the extended range usage).

   hex_pitch7bits.fractionalPitch25bits_base32
       The 7-bit integer part (in hexadecimal) for semitone pitch, ranging from 00 to 8F.
       A 25-bit fractional part for microtonal precision, expressed in base 32 using the characters 0–9 and A–V. This base-32 representation spans values from 00000 (zero fraction) up to a maximum that encodes all 2^25 subdivisions of a semitone.

An example line might be:

16 8F 8F.VVVVV

   16 = MIDI channel 16
   8F = MIDI note number in hex (143 in decimal)
   8F.VVVVV = 7-bit pitch = 8F (in hex), fractional part = VVVVV (in base 32)

Purpose and Implementation

Chanopif’s primary objective is to facilitate unambiguous, universal microtonal tunings within the MIDI 2.0 ecosystem. By standardizing on 402,653,184-EDO, Chanopif ensures that any note pitch, however finely tuned, can be represented consistently in .cnpf files.

   High Precision: At around 1.49 × 10^-6 cents per step, the resolution far exceeds what the human ear can typically discern, making it suitable for studio recording, live performance, or any scenario requiring advanced microtonal control.
   Compatibility: Although the full 25 bits of fractional pitch may not be supported universally, MIDI 2.0 recommends supporting at least 9 bits, ensuring backward compatibility.
   Persistence of Tuning: Once a note’s Pitch 7.25 is set via Chanopif instructions, it remains in effect for subsequent notes unless overridden by other tuning data.

Significance

   Standardized Microtonal Implementation: By adopting a consistent 402,653,184-EDO approach, Chanopif eliminates ambiguity over how fractional pitches are interpreted.
   Widespread Applications: It can be used to develop new instruments, experiment with alternative scales, or achieve hyper-accurate tuning in classical, jazz, electronic, or any musical style.
   Future-Proof: Chanopif is designed to scale with evolving MIDI technology, leveraging the expanded channel range (up to 256) and high-definition capabilities of MIDI 2.0.