Here is another form of ornamentation which pipers call a shiver.
This ornamentation is an alternative to the double cran on the e or f sharp, but on the English can be played on any note if so desired,.
It consists ofthe melody note cut by the note above. On the English concertina that would be f sharp cut by g. so instead of an f sharp you would have F G F G F, its very similiar to a fiddlers trill.   Dick Miles