You can use Siri's voice by typing text into a text-to-speech (TTS) engine that uses Siri's voice. Here are the general steps:

On macOS:

1. The say command on macOS is used to convert text to audible speech. If you want to convert the contents of a text file to an audio file (e.g., MP3), you'll need to use additional tools since the say command itself doesn't have an option for outputting to an audio file.

   You can use a combination of the say command and the text2wave command to achieve this. Here's an example:

   say -o output.aiff -f file.txt

   This command will use the say command to convert the text in file.txt to an AIFF audio file named output.aiff. To convert it to MP3, you'll need an additional tool like ffmpeg. Make sure you have ffmpeg installed; you can install it using a package manager like Homebrew:

   brew install ffmpeg

   Once ffmpeg is installed, you can convert the AIFF file to MP3 using the following command:

   ffmpeg -i output.aiff -codec:a libmp3lame -qscale:a 2 file.mp3

   This command will take the output.aiff file and convert it to an MP3 file named file.mp3.

   So, the complete process would be:

   say -o output.aiff -f file.txt
   ffmpeg -i output.aiff -codec:a libmp3lame -qscale:a 2 file.mp3

   This will convert the text in file.txt to an MP3 file named file.mp3. Adjust the filenames and paths as needed for your specific use case.