Antares autotune is probably the software they use you can hear it everywhere these days.I always get a laugh when I hear these boy/girl wonders doing it live without the studio technology they are totally woegeous yet they really believe their own marketing hype they probably think singing in demi-semi tone scales is the norm and to be fair they are true innovators who have brought to music and made commonplace such wonderful vocal harmonies as A flat tormented or D sharp extinguished.

As for the pseudo Celtic crap I think a lot of people hearing commercialised music that borrows aspects of Celtic traditional music may be put off thinking that these examples are indicative of Celtic music generally.Personally I'm sick of this "my grannies budgies cousin is Scottish/Irish/Welsh/Breton and they taught me this song"that I see so often these days.Any old crap can get away with being called Celtic these days if it has a bit of uillean pipes and a few bars of generally badly played feadag particularly of your surname starts with O' or Mac.