Joining four piece back
My technique for joining pre thicknessed backs is shown in my web page https://www.sobellguitars.com/brazilian-rosewood-for-sale/
In the very early 1990s I built a Brazilian rosewood Model 1 guitar for Martin Simpson. For back and sides I used some special Brazilian rosewood I’d bought from a Dutch builder who was selling his stock. I’ve no idea exactly how old it was, but it was clear it was ancient. And some of it outstanding quality.
The wood I picked for Martin was a four piece back; the number of pieces the back is made up from is unimportant, the quality of the wood is what matters. This Model 1 was Martin’s main guitar for many years; he still has it and will never sell it.
I’m now building a Martin Simpson model with an identical set from the same old Dutch stock. I sanded it to thickness in its component pieces, and joined them later. Joining a four piece back this way is more time consuming but works perfectly.
Here is the back joined, reinforced with spruce, and