Published 2024-10-28.
Time to read: 2 minutes.
av_studio collection.
I decided to write a small Ruby program to generate MIDI files. See How Pro Tools Imports MIDI Files for the motivation for doing this.
About Middle C
In Pro Tools and Ableton Live, middle C is known as C3. See a discussion about middle C, and this article.
Creating the Ruby Gem Scaffold
I used the F/OSS nugem command-line program
that I published a few years ago to create the scaffold for my new Ruby gem.
I did not use nugem’s --executable option,
because the current version of nugem generates code for Thor instead of OptionParse.
Previously, I discussed why most people should not use Thor to generate command-line skeletons.
One day I will update nugem to generate scaffolding for OptionParse instead of Thor.
You can inspect
the OptionParse code that I wrote for midi_create.
$ nugem plain midi_create Creating a scaffold for a new plain Ruby gem named midi_create in /mnt/f/work/ruby/my_gems/generated/midi_create. Creating the local git repository Initialized empty Git repository in /mnt/f/work/ruby/my_gems/generated/midi_create/.git/ Do you want to create a repository on GitHub named midi_create? (y/N) y Creating a remote #<struct Nugem::Repository::Host domain="github.com" , camel_case="GitHub" , id=:github> repository Pushing initial commit to remote #<struct Nugem::Repository::Host domain="github.com" , camel_case="GitHub" , id=:github> repository Enumerating objects: 32, done. Counting objects: 100% (32/32), done. Delta compression using up to 24 threads Compressing objects: 100% (29/29), done. Writing objects: 100% (32/32), 8.09 KiB | 188.00 KiB/s, done. Total 32 (delta 0), reused 0 (delta 0), pack-reused 0 (from 0) To github.com:mslinn/midi_create.git * [new branch] master -> master branch 'master' set up to track 'origin/master'. The midi_create gem was successfully created. There are no TODOs. You can run 'bundle install' from within your new gem project now.
midilib
After looking at available Ruby gems
I decided to try midilib
to create the empty MIDI files.
It has 34 forks and 181 stars.
midilib can read and write MIDI files in two common flavors of MIDI:
- Format 0 (a single track)
- Format 1 (multiple tracks)
By default, midilib writes format 1, which is the most common format.
MIDI file format 2 is not yet supported, and it is rarely seen in the wild at the time of writing.
The Completed Program
The midi_create repo on GitHub contains the source code.
Assuming you have installed Ruby on your computer,
you could install midi_create by typing the following at a shell prompt:
$ gem install midi_create
If you are running rbenv (and you should, according to the instructions mentioned above), type:
$ rbenv rehash
This is the help message:
$ midi_create -h midi_create: Creates a MIDI file containing an 8-note scale in the key of C, starting at middle C (C3 in Pro Tools and Ableton Live). Syntax: midi_create [Options] PATH_TO_MIDI_FILE Options: -b 120 Specify beats per minute (BPM); default is 120 bpm. Only integers can be used; a decimal point will cause an error. -f Overwrite the output file if present -t NAME Use this title for the track -h Show this help message
Sample Usage
Create a MIDI type 1 file called filename.mid with one track in the current directory, without a title.
Fail if the file already exists.
Include an 8-note scale in the key of C major, starting at middle C (C3).
$ midi_create filename.mid
Like the previous example, but overwrite filename.mid if it already exists:
$ midi_create -f filename.mid
Like the previous example, plus include the title Test MIDI clip for the track. Ableton Live ignores the MIDI track title, but Guitar Pro uses it.
$ midi_create -ft 'Test MIDI clip' filename.mid
Like the previous example, plus set the beats per minute (BPM) to 150. BPM can only be specified as an integer; using a decimal point will cause an error.
$ midi_create -b 150 -ft 'Test MIDI clip' filename.mid
