I use a G single-row accordion often in my zydeco band. It's lowwww, bro. Most of the zydeco tunes I play it on are in the key of D(cross-harp.) The single-row is not as limited to one key as many folks might think. I've seen Marc Savoy play one song in three different keys on a single-row. In his hands, it's an amazing and versatile instrument. Check out his video, "The Gospel Accordion To Marc." Of course after watching him play, it's going to be either inspirational or will cause you to drink heavily. Either way, you'll catch a good buzz! And the more you drink, the better you'll sound.
I had a chance to play one of those low G accordions. Hardly any bellows movement and that thing growls. I have a very old Eagle in F that I picked up for next to nothing. Very high. Can't imagine a G box above that without driving all the neighborhood dogs crazy.
Steve
Similar to what Steve just mentioned, I have a G box and the note are at least an octive above the G scale on my C box.
It is not a Cajun accordion and only has two reed banks. It is old and of Chech manufacture. I suspect it was use for traditiojnal Eastern Europian music or perhaps Irish jigs and hornpipes.
It was an "I will trade some of my junk for some of your junk" swap and should make an interesting restoration project someday.