Zeno, first of all thanks a lot for sharing these historic rarites. It must have been a great thrill to find these discs. I sent a link to your site to Cristobal Diaz Ayala, those recordings are not even listed in his comprehensive discography, I am sure he will be glad to have that info.
To compare the vocalists, I listened to the CD called "Santero" which Ayala's discography says was originally recorded in 1947-48, and features (the more famous?) Merceditas Valdés (you can listen at the link below). Especially the song "Yemaya," which you can hear at the link below:
http://www.goear.com/listen/f69e58a/yemaya-merceditas-valdesAt 00:59 Mercedes begins singing "Yemaya e, olodo awo yo Yemayá" which the vocalist on the SMC recordings begins singing at 2:27 (a bit oddly, this song is introduced by the coro a few seconds earlier).
To me it is clearly not the same person on the SMC record, Merceditas Valdes has a more full-throated voice and somehow more professional...the singer on the SMC recording is more nasal and more casual, natural sounding. I like them both, they just don't sound the same.
Interesting info about the "other" "Mercedita" Valdés, I wasn't aware of that.
However, I believe the adding or dropping of the "s" at the end is more a factor of Cuban speech patterns and lack of careful notation that about distinguishing one performer from another. I see (the more famous?) Merceditas Valdés written both ways, and also sometimes as "Mercedes Valdés."
[EDIT:]Orovio's dictionary of Cuban music has it as "Mercedita," Radamés Giro's Diccionario Enciclopédico has it as "Merceditas" (with an "s"). (They also give completely different birth dates, for what that's worth!)
If I am correct though, the whole notion that the singer on the SMC recordings could be Mercedes Valdés is based on mistaking the players on the Mongo session, is that right? So it could be anyone really.
It would be great to nail down the players on this session. I see Carlos Vidal died in Los Angeles in 1996, maybe some of you guys on the west coast could track down someone who knew him, maybe he talked about it before. There is a video of him on youtube in 1994 with a group called the Estrada Brothers Latin Jazz Sextet:
http://www.youtube.com/watch?v=bMA2eyyD0GEOne other question I have, about the dates of the sessions, you wrote they were recorded "circa 1948".
Ayala says the Chano Pozo sides were done on Feb 4 1947. The catalog numbers are 2517 and 2518 and the titles are "Ritmo Afro-cubano 1 - 4."
The Vidal Bolados sides are numbered 2519 and 2520 and entitled "Ritmo Afro-cubano 5-8." So couldn't we assume that they must have been recorded very close to the same time, maybe even at the same session, with some of the same players?
For example, I am pretty sure the singers of the columbias Nos 4 & 5 are the same person. (BTW your transfers sound much better than the ones on the Tumbao reissue, I have to say.) Maybe the Tumbao booklet that came with the Chano Box set lists the personnel? I don't have it at hand at the moment.
Saludos
Barry