I'm not sure how it was done in the 50's. But I watched the painter at the Gibson CS do a row of R9's. I took what I learned from that and also kept my ears open here and at other forums and have done a few bursts myself. This is what I've found works.
All bursts obviously start with a yellow base of course. Then a light burst is sprayed with a mix of blue and amber dyes. Then the final burst color is applied. Whether it be washed cherry, teaburst, vintage dark brown, it always has the blue/amber mix which you can sometimes see peaking thru the inner edge of the burst gradation to yellow. The last step is an ambered clear coat is applied.
To do a lemon burst, you just skip the third step. The variations in shades of lemonburst is due to slight mix changes, and the maple its going on. Some maple is lighter, and some take to colors differently.
This was my last one. I went a bit deeper with the lemon to get a more of a honey burst.