Metrome

Metrome is a click track generator. It uses simple text-based rhythm notation to generate any kind of rhythmic click track. Metrome currently can be used as a CLI or as a Rust crate. A web interface is in the plans!

Why would you use Metrome when you can use a metronome?

Your rhythmic needs may differ. For most musicians, a simple device that beats constant pulses may be enough. For a small portion of musicians, a polyrhythmic metronome may serve their niche rhythmic needs. However, if you find yourself facing pieces with constant tempo, meter and pulse changes, you might want to have dedicated click track for practicing the piece. Heck, even pieces with the occasional odd time signature will mess up practicing with a normal metronome.

Usage

CLI

System requirements: you will need Rust to run the Metrome CLI. Follow this page to install Rust.

Quickstart

For a quick start, you can clone this repo and render the examples.

git clone https://github.com/somecho/metrome
cd metrome
# Linux & Mac
./render_examples.sh
# Windows
./render_examples.ps1

After running this, the root of the metrome directory should now contain many WAV files which you can run directly in the command line with cvlc if you have VLC player installed. Otherwise, just play the WAV files in your player of choice.

Providing your own score

The Metrome score is just a textfile with no extensions. To provide your own score to Metrome, simple use the -p flag like such: metrome -p my_score or cargo run -- -p my_score in the metrome project directory. Use the -o/--output flag to specify a custom output path. For more information on how to write a rhythm score, read the following section.

Programmatic Usage Example

use metrome::{scanner, score::Score};

fn main() {
    let file = std::fs::read_to_string("myscore").unwrap();
    let tokens = scanner::scan(file).unwrap();
    let score = Score::new(tokens).unwrap();
    score.write_click_track("myscore.wav");
}

The Metrome Score

The score metrome uses to create click track is just a simple text file. Here's a short example of what it looks like.

Example:

| q. e q. e    | e e e e h 
| q. e q. e    | e e e e h 
| q q. e e e   | e e q. e e e
| e e q. e e e | e e q. e e e | 

Bars

As you can see, it follows traditional notation in that notes are grouped in bars (as denoted by the barlines | ). However, unlike traditional notation, you do not need to provide a time signature. Bars serve the purpose of differentiating strong and weak beats, with the first beat of every bar strong and the rest weak.

| q  q  q |
  ^  ^  ^
  |  |  |
  |  |  Weak
  |  Weak
  Strong

⚠ every score must begin and end with a barline!

Tip: you can organize your score however you like. Line breaks do not make a difference.

Notes, Durations and Ratios

Notes can be represented using these letters:

• w - whole note
• h - half note
• q - quarter note
• e - eighth note
• s - sixteenth note
• t - thirtysecond note

Alternatively, you can also write notes using ratios:

these two bars are the same: | 1/4 1/4 1/4 1/4 | q q q q |
ratios are great for triples: | 1/6 1/6 1/6 1/6 1/6 1/6 | 

You can use any combination of this. For example, | q 1/6 1/6 1/6 h | is a valid bar.

Dotted Notes

Any note, duration or ratio can be extended using dots ., just like in traditional notation. For example, q. is as long as 3/8 and q.. is as long as 7/16.

Tempo

Tempo can be specified like this q = 140 (read: 140 quarter notes per minute). The grammar for this is <note> = <number>, where <note> is either a duration represented as a letter or a ratio.

The tempo can be specified anywhere within a score:

At the beginning like a normal score
q = 140
| q q q q |

After a bar 
| q q q q | h = 90 h h |

In the middle of a bar like a psycho
| q q q=150 1/6 1/6 1/6 |

Note: When no tempo is specified, the Metrome defaults to q = 120 or 120 quarter notes per minute. Pretty sane if you ask me.

Relative Tempo Changes

In many music, tempo changes can be done relatively. For example, ♩=♩. , meaning dotted quarter notes are now as long as quarter notes. You will commonly find this in music that switched from 4/4 (simple time) to 6/8 (compound time), where the pulse division turns from two to three stays the same length.

In Metrome, the equivalent is q=q.. Simple, clean. You can do all sorts of wild things. You can also do this 1/6=q, where the quarter notes are now as fast as the triplet quarter notes (essentially the same thing, but semantically and musically different.

Examples

Check out the examples for reference.

Roadmap

• take stdin input
• floating point tempo
• -o flag for specifying custom output path

---

© 2024 Somē Cho