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miditempo script

This PERL script changes or lists the tempo on piano-roll MIDI files.

The tempo is handled differently than in a typical MIDI files. Ticks in the MIDI files are equivalent to pixel rows in the original image (starting at the first note/expression hole on the roll). The tempo is not controlled directly by tempo meta messages, but rather the ticks per quarter note value in the MIDI file header. For a 300 DPI scan, the tpq value is six times the tempo.

Tempo meta-messages are used to emulate the roll acceleration. These tempo meta-messages do not change when changing the tempo using this script. The accelleration is set to 0.4%/foot (0.4%/3600 ticks).

The binasc program needs to be installed before using this script. It can be found in https://github.com/craigsapp/midifile .

Installation

To install the script in /usr/local/bin type the command:

git clone https://github.com/pianoroll/miditempo
cd miditempo
make install

The binasc program is required by this script. To install from github, type these commands in the terminal:

git clone https://github.com/craigsapp/binasc
cd binasc
make
make install

The last step will copy the executable program to /usr/local/bin. Type the command:

which binasc

to verify that the shell can see it; if so, then you should be ready to use the miditempo script to change tempos of pianoroll MIDI files.

Options

Option Description
-s # Set the tempo to # (such as "-s 100" to set the tempo to 100).
-l List the current tempo of the MIDI file(s).
-o Overwrite original MIDI file with new tempo version.
-r Use red welte tempo (98.4251968504 -> 98.5).

Examples

  • To change the tempo of a MIDI file to the default Red-Welte tempo:
miditempo -ro file.mid
  • To change all tempos in multipl files to default Red-Welte tempo:
miditempo -ro *.mid
  • To set the tempo of a MIDI file to 100:
miditempo -s 100 file.mid
  • To list tempo in a file:
miditempo -l file.mid
  • To list tempos in multiple files:
miditempo -l *.mid

Caveats

This script will need to be updated for MIDI files that are derived from scans of DEA rolls (or any roll scanned at the higher camera position).