I took this blurred image of M13:
and looked at the pixel values (representing brightness in the SDSS u band) along column 115, which cuts more-or-less down the brightest part of the image.
I then created three sound files. The first (shown in red in the plot below) represents the brightness of the pixel. The second (shown in green in the plot below) represents the change in the brightness (1st derivative). The third (shown in blue in the plot below) represents changes in the changes in the brightness (2nd derivative).
I've scaled all of the data to fall within a frequency range of 100-200 Hz, which is the y-axis of the plot. The x-axis is the row number.
Once all three sound files were made, I mixed them into a single track. Wear earphones for the best effect:
M13 Brightness Changes
What do you hear?