I have heard a bit of Sprechstimme by now--that's Schoenberg's invention of speaking set to music. I think if memory serves that it first appears in Gurrelieder (1901/11 [I think written around 1901 and orchestrated closer to 1911--He's supposed to have forgotten how to orchestrate in Mahler's style by then and had to revive a long abandoned technique.]), the orchestrated song cycle that Schoenberg wrote while he was still in his Mahler phase. In the performance of Gurrelieder I heard at the San Francisco Symphony Hans Hotter performed the Sprechstimme. His was very speech-like.
Sprechstimme is notated like normal vocal music, except where the note heads would normally appear are X's. This leaves the performer with a wide range of options, extending from normal speech set to music, sometimes called melodrama, to something that sounds a lot like singing. Hotter was like a magnificent old actor. His motivation in performing the part seemed rather like mine--voice is shot, but I can still do Sprechstimme. He was the best I've heard.
The main later examples are Pierrot Lunaire (1912) and Moses und Aron (1930/32). My theory is that Schoenberg was as bored by Moses as we are listening to it, and this is why it was never finished. He turned out to be not as high minded as he thought he was. According to this article in Wikipedia there is Sprechstimme in Wozzeck and Lulu. So I missed that as a texture.
I think Pierrot Lunaire is the only one that is regularly performed by sopranos who seem to want to sing. The Christine Schaefer Pierrot Lunaire quite often sounds like out of tune singing. Deliberately out of tune--it's clear this isn't an accident. I would be curious to hear a female perform this in a more talky style. Maybe they are trying too hard to come close to the notated pitches. I think only the general contour is required.
I have decided this article would be far better with a few examples. First we have Hans Hotter's wonderful example from Gurrelieder.
Here is a very nice clip from Moses und Aron. One sings, the other doesn't. The two brothers alternate, thus giving a very clear idea of the difference between Sprechstimme and singing.
I openly admit to a mania for this film of Pierrot Lunaire with Christine Schaefer.
Anyway, that should give you the idea.