Audible DRM Removal for personal use

For MP3, try eyeD3, found in this SO answer.

  --add-image=IMG_PATH:TYPE[:DESCRIPTION]
                      Add an image to the tag.  The description and type
                      optional, but when used, both ':' delimiters must be
                      present.  The type MUST be an string that corresponds
                      to one given with --list-image-types. If the IMG_PATH
                      value is empty the APIC frame with TYPE is removed.

For Ogg, there's vorbiscomment. It doesn't support loading image files out of the box, but a cover art tag in Vorbis is just an image file encoded in base64, stored in the COVERART tag and its mimetype in COVERARTMIME - something like

coverart=$(base64 $jpegfile)
vorbiscomment -a -t 'COVERART=$coverart' -t 'COVERARTMIME=image/jpeg' $infile $outfile

First install mp3info, it should be in the repositories of your distribution (you have not said, so I assume you are using Linux of some sort). If you have a debian-based distribution, you can do so with

sudo apt-get install mp3info

Once mp3info is installed, you can search the directory music for songs of a certain length with this command:

find music/ -name "*mp3" | 
  while IFS= read -r f; do 
   length=$(mp3info -p "%S" "$f"); 
   if [[ "$length" -ge "180" && "$length" -le "195" ]]; then 
     echo "$f"; 
   fi;  
done

The command above will search music/ for mp3 files, and print their name and length if that length is grater or equal to 180 seconds (3:00) and less than or equal to 195 seconds (3:15). See man mp3info for more details on its output format.

If you want to be able to enter times in MM:SS format, it gets a bit more complex:

#!/usr/bin/env bash

## Convert MM:SS to seconds.
## The date is random, you can use your birthday if you want.
## The important part is not specifying a time so that 00:00:00
## is returned.
d=$(date -d "1/1/2013" +%s);

## Now add the number of minutes and seconds
## you give as the first argument
min=$(date -d "1/1/2013 00:$1" +%s);
## The same for the second arument
max=$(date -d "1/1/2013 00:$2" +%s);

## Search the target directory for files
## of the correct length.
find "$3" -name "*mp3" | 
  while IFS= read -r file; do 
   length=$(mp3info -p "%m:%s" "$file"); 
   ## Convert the actual length of the song (mm:ss format)
   ## to seconds so it can be compared.
   lengthsec=$(date -d "1/1/2013 00:$length" +%s);

   ## Compare the length to the $min and $max
   if [[ ($lengthsec -ge $min ) && ($lengthsec -le $max ) ]]; then 
       echo "$file"; 
   fi; 
done

Save the script above as findmp3 and run it like this:

findmp3 3:00 3:15 music/