here is a tip for treble side playing,in fiddle music [scottish] there is a bowing ornament called a burl in irish music it is called a treble, on accordions and concertinas this is best copied by cross fingering, it can be used in jigs and reels and marches, it is best practised by using it in a scale, then go and listen to fiddle players use it on you tube in tutorials, the only thing you will not achieve is the scatch, but that is the point[where they scratch] to exert a little more bellows pressure. Dick Miles