I found it absolutely remarkable because of what he says on it. He starts off with some light-hearted verse in English, followed by a trivial poem in German, a few sentences of Latin, and the Marseillaise (the song of the French Revolution and the current French national anthem) in French.
Bismarck has a reputation of being Germany's first militaristic leader in modern times – which he certainly was, but the British and the French in particular were not exactly pacifists with their battle for global colonialist hegemony. If anything, Bismarck has gone down in history for his Blood and Iron approach because it proved successful; at a time when soldiers stood in a row facing each other because they had to load their muskets standing, Bismarck sent in an army with the first rear-loading rifles, allowing his soldiers not only to re-load their guns faster, but also do so lying down.
It also does not help that we perforce view history in reverse, so it's hard to see anything German in the 19th century without interpreting it as part of the fatal developments that eventually led to the disaster of Nazism.
True, Bismarck reunited the Protestant northern and Catholic southern German states, thereby creating a single Germany that could be a dominant force, but as this audio recording shows, Bismarck was not a Führer, but a cosmopolitan who spoke several languages, enjoyed the good life and, when he had the chance, chose to record himself for posterity with a display of his linguistic talents – and his penchant for light humor.
The recording ends with some advice to his son: don't work too much, but don't eat or drink too much either. Good idea. Sounds like Otto was the kind of guy you might want to have a beer with.