Hello Michael,
To slow down the audio without altering the pitch, you can use a phase vocoder or time-stretching algorithm. MATLAB does not have a built-in phase vocoder function, but you can use the audioExample function from the Audio System Toolbox, or implement a basic time-stretching algorithm. Please follow this link to know more: https://www.mathworks.com/help/audio/ref/stretchaudio.html
I hope this helps!
