Why can I not use findpeaks with this audio signal?

Honestly not used the software much at all I understand this may be a very simple problem. My aim is to spectrally analyse an audio signal and extract its modes (frequency peaks) to spectrally model in max msp. Also if anyone knows a better way to find out the frequencies and amplitudes of peaks of an audio signal please let me know. Below is the code that will not work, I have also attached the audio sample I would like to analyze:

clear;
clc;
close all;
[audio_file, Fs] = audioread("honours_gun.wav");
findpeaks(audio_file);

Below is the error it returns:

Error using findpeaks

Expected Y to be a vector.

Error in findpeaks>parse_inputs (line 199)

validateattributes(Yin,{'double','single'},{'nonempty','real','vector'},...

Error in findpeaks (line 136)

= parse_inputs(isInMATLAB,Yin,varargin{:});

Error in Test (line 5)

findpeaks(audio_file);

Answer 1

[Star Strider]

The findpeaks function takes a vector input for the first argument. Note that ‘audio_file’ is a (8447 x 2) (stereophonic) matrix.

Use:

findpeaks(audio_file(:,1));

or

findpeaks(audio_file(:,2));

instead.

I doubt that you will get any useful information from using findpeaks as you are, with no additional arguments.