Creating a master file

Hi guys,
I hope you are well and can help.

I have many text files, all with the same  format, that contain, as part of their file names, "summary_sorted.txt".
For example, summary_sorted_a_.txt,  summary_sorted_b.txt, summary_sorted_c.txt etc etc.

The format of each of these files is as follows:

--------------------------------------------------------------------------------------------------- summary_sorted_a.txt
abalone, adversary, aeroplane, at the park;

--------------------------------------------------------------------------------------------------- summary_sorted_b.txt
bat, benign, bipartisan;

I'd like to produce a script that will....

Examine each summary_sorted.txt file.
For each file examined, treat each file examined as 1 line, and copy its entire contents to a new file called master.txt. and
then add a blank line after its pasted contents, before the script goes on to look at the next summary_sorted.txt file.

As an example of what a master.txt file would look like based on the above, would be:

--------------------------------------------------------------------------------------------------- master.txt
abalone, adversary, aeroplane, at the park;

bat, benign, bipartisan;

Any help greatly appreciated.