@John @a An alias won't work - you'll need to add a bash function; cat() { ffmpeg -v quiet -f data -i "$1" -map 0 -f data - ; }

Unfortunately, such trivial function doesn't operate as a concatenate program, to achieve that, you need to add a bash loop as below;
cat() { for argument ; do ffmpeg -v quiet -f data -i "$argument" -map 0 -f data - ; done ; }