Problem:

I want to make playlist with songs that have similar “velocity”. The metric is bpm (beats per minute). So manually you can edit bpm field info for each file; but how can calculate bpm and tag for all files automatically?

Solution:

To solve it, you can make execute a script that use the bpm-tools in Ubuntu. Before use the script, all your directories and mp3 filenames should not contain any spaces; spaces will be replaced with _ using another two scripts.

Step by step:

  1. Install the required packages. Open a Terminal and type: 
    sudo apt-get install bpm-tools
sudo apt-get install libsox-fmt-mp3
  2. Rename all the directories in your music folder. This will replace spaces in the filename. 
    find . -type d -name "* *" -follow -print | while read file; do echo "$file" new name is: ${file// /_}; mv "$file" ${file// /_}; done
  3. Rename all the directories in your music folder. This will replace spaces in the filename. 
    find . -type f -name "* *" -follow -print | while read file; do echo "$file" new name is: ${file// /_}; mv "$file" ${file// /_}; done
  4. Download the file here or create it as a new file, use this name: get-bpm-current-folder.sh. Type these lines inside:
#!/bin/bash
#author: Rogelio Prieto Alvarado
#22/march/2022
#Objective: calculate the bpm for each mp3 in this directory or any subdirectories. Tag each file (mp3 tag).

#initialize counter variable
counter_file=0
#process each .mp3 file
while read -r line ; do
	echo "=============="
    #incrementar el contador de archivos.
    counter_file=$(($counter_file+1))
	#show filename
    echo $counter_file.file:\"$line\"

    #add quotes at begin and end
    #line=$(echo \"$line\")
    #echo "line=$line"
    bpm-tag $line
    #echo \"$line\" | echo

done <<< "$(find . -name '*.mp3'   -type f  -follow -print)"
#explanation about this subshell: https://stackoverflow.com/questions/16854280/a-variable-modified-inside-a-while-loop-is-not-remembered
echo "=============="
echo "=============="
echo $counter_file"  .mp3 files were analyzed."

Change the permissions to execute, type:

chmod +x get-bpm-current-folder.sh

Execute the script:

./get-bpm-current-folder.sh

Source:

https://askubuntu.com/questions/86113/how-can-i-detect-the-bpm-beats-per-minute-of-a-song
http://manpages.ubuntu.com/manpages/focal/man1/bpm.1.html
http://mywiki.wooledge.org/ParsingLs
https://stackoverflow.com/questions/105212/recursively-list-all-files-in-a-directory-including-files-in-symlink-directories
https://stackoverflow.com/questions/16317961/how-to-process-each-output-line-in-a-loop https://stackoverflow.com/questions/44050676/find-files-with-spaces-in-the-bash
https://stackoverflow.com/questions/16854280/a-variable-modified-inside-a-while-loop-is-not-remembered\