78s

And more of these...

Back in the day many classically trained opera singers did do also these popular songs, sometimes under a pseudonym. Georg Malmsten of course effectively switched completely to popular music, while e.g. Ture Ara and Sulo Sala did both. Sulo Sala in general seems to be mostly forgotten nowadays (apparently there were no major hits for him), a shame since what I have heard of him I have liked.
And then again there were singers with no classical training, like A. Aimo.

Here Ture Ara performs a traditional Karelian folk song in early 30s, with an interesting mixture of bombast and melancholy:
Ture Ara: Reppurin laulu / Vallinkorvan laulu
http://www.mediafire.com/?zjezwjnyjmm

And a split single from mid-40s,
A. Aimo / Sulo Sala: Ruusuja hopeamaljassa / Suo mulle hymysi Maria
http://www.mediafire.com/?amkqzdmmzne

And Finnish 78s

Split single from mid-40s, one cheerful, one melancholic:
A. Aimo - Aamu Airistolla / Georg Malmsten - Erokirje heilille
http://www.megaupload.com/?d=RMZYT69K
http://www.mediafire.com/?ftoygmmlytn

Lumberjack romanticism from a singer quartet, early 50s
Kipparikvartetti - On lautalla pienoinen kahvila / Tukkipoika porskuttaapi
http://www.megaupload.com/?d=8QWZ3RR6
http://www.mediafire.com/?2quyjydwhqy

More Finnish 78s

Ture Ara: Emma/Villiruusu, hit single from 1929

http://www.mediafire.com/?miz2ci1yizt

A. Aimo: Uraliin/Iso Antti, jaunty WWII propaganda

http://www.mediafire.com/?ljdgy41bjh4