Complex sentence: The sound developed it by the group has been assigned to the kind "Tribal" and "Celtic Rock" and their songs have contributed and they contribute today to the classical traditional scottish music, together with the bluegrass, rockabilly and others.
Split into simpler sentences: The sound developed by the group has been assigned as "Tribal" and "Celtic Rock". Their songs contribute to the classical traditional Scottish music, together with the bluegrass, rockabilly and others.