Chris is correct, in a since, you just bring down all of the reeds one row, then put a regular set of Bb's at the number 10 row. In my new quest to build accordions my plan is to make all of the Bb's this way. Takes a bit more time to do but it is still very loud and powerful, as Chris says the "timbre" is like that of a C. Thanks Chris, new word for the day !

completely clear, Rusty and Chris.

Funny thing is that I think that the C reeds of a Castagnari one row (Antonelli a mano reeds) I posessed were shorter than the Binci's. (so simular story as your Bb) But I have to measure.
Which is sure that the antonelli's had a direct (fast, loud) tone, but with a short time duration/ no echo when stopped; dry sound. But this is non scientific subjective...
Somebody called it an 'old sound' referring to the older instruments (John Delafosse maybe; while they had big reeds, I heard).
One thing was extraordinary. I never had to retune them for more that 8 years. Reeds looked very sturdy too. (they are now in an Eric Martin cajun accordion, and this proves that the construction also makes a cajun sound, the castagnari wasn't really cajun, the martin 100%)
Gus

To anyone else with Martin boxes.... is yours set up MLMH too?

I wonder if he had to set it up like this because I had its switched from Binci to Salpa.

It is really bizarre but the first set of mid reeds are definately longer than the lows.

What is done about button number one?

You would put a regular set of Bb reeds on the number one row. Since this row is such a low and "bassy" tone, a difference in sound can barely be heard.

If anyone says they can tell you the brand of an accordion by just listening to it and not seeing it. They are dealing in falshoods.

I do know that hand made accordions are never 100% alike. I do know that certain builders have certain ways of tuning the reeds. I'm not talking about wet/dry.

People may say that Salpas sound brighter than Bincis. I think it all depends on how the maker tunes the reeds. I've got 2 accordions with Bincis of the same brand.

They sound way brighter than a different brand that has Salpas. In fact one of the reasons I wanted to have the Bincis out of this accordion is because I didn't recognize the sound I'm used to.

The brands of accordions I mentioned, I have played extensively enough to know what they sound like. I couldn't name them by means of a recording, but I know the style of tuning.

From listening to thousands of hours of playing my different brand Cajun accordions, this is not true at all.

I don't even know if brighter is the right word... Maybe crystal clear, maybe even thinner in someone elses opinion.

Maybe thinner is the word. I don't know enough about tuning reeds to presume, but my favorite builder has written about tuning reeds, but never ever specified how he does it "by ear" to me.

Perhaps the reeds in my favoritve accordions have been scraped "thin" enough to sound brighter?

I don't know how it's done, but I know I've heard Bincis sound different in different brands. In fact, VERY different.