In all honesty, I can't see who in their right minds would prefer an English Concertina over an Ondes Marteno, especially for the accompaniment of Scotch Ballads. Indeed, I'd go one further and say the ideal instrument in this respect would a THEREMIN.

Patented in 1928 (the same year the Ondes Marteno was invented) the theremin would become one of the instruments of choice for legendary Northumbrian dance band-leader, trumpeter, percussionist, & early electonic music pioneer Fred Fauntleroy (obit. 1951). Indeed, Fred abandoned his celebrated musical saw on being gifted a theremin by then Lady Coldharbour, Letitia Wetherstone, at some point in the mid 1930s and used it thereafter at the Hallowe'en Balls at Coldharbour Castle where it could be heard to great effect on his renderings of such gruesome epics as Tam Lin, King Henry and The Witch Mother.

Whilst Fred never played the Ondes Marteno himself, he acquired one for his piano player (Guy Zance) and the two would provide eery electronic duets (to the accompanyment of several droning Northumbrian Smallpipes, various jungle drums & gamelan instruments) in the resonant pillar hall of Coldharbour whilst their aristocratic guests would process from their rooms in togas, smoke excessive amounts of marijuana and proceed to freak out in an orgy of dimly-lit pagan depravity in a scene more typical of 1960s San Francisco than 1930s Northumberland, though, in actuality, inspired by the debauched antics of Emperor Gaius Julius Caesar Augustus Germanicus, AKA Caligula, who was greatly revered by Aristocratic Northumbrian Mystics, Occultists, Gnostics, Devil Worshippers and Mithraic Pagans at the time.

Of course, both the Theremin and Ondes Marteno were unknown to Caligula, but had they been one can be assured he would have prefered their demonic & less-than homely timbres over the tediously insipid folksy honking of the English Concertina any day and seized upon both with great gusto. Just check this out:

http://www.youtube.com/watch?v=OdL-vbOwvL0