That said, it's littered with inaccuracies that I don't think we would tolerate if this were one of Vi Hart's math videos. Most egregiously, I think, is that she wrongly ascribes some of Schoenberg's dogma to Stravinsky: Stravinsky never had much to say about the desirability of conditioning children to understand dodecaphonic music intuitively (Schoenberg may not have either -- if I had my copy of Strunk's Source Readings in Music History on me right now I could verify this, but if I remember correctly it was either Webern or an unrelated third party who promulgated this particular vision of the ascendancy of avant garde music), nor was he particularly committed to using all twelve tones in his tone rows -- Agon, one of his most famous serialist works, employs a seventeen-tone row at one point [1]. Early on in the video, she selects a tone row at random and sort of dismissively asserts that no one would be able to tell the difference anyway. This is frustrating, because masters like Schoenberg did in fact order their rows to ensure not only structural but sonic coherence, using techniques such as hexachordal combinatoriality [2]. Now, that's not to say that these considerations are audible to most listeners -- one of serialism's greatest failings, in my opinion, is that much of its content is only discoverable on paper even by highly trained musicians -- but it's certainly audible to some, and it's worth noting that this runs counter to her assertion that musical lines don't have meaning until they're embedded in a harmonic context: it's not even true with serialism as practiced! It's certainly the case that many melodic lines can make sense in multiple harmonic contexts, but the idea that melodies imply their supporting harmony has been a foundational concept in Western music since at least the Baroque, and to counter otherwise is absurd -- otherwise we would be unable to comprehend the harmonic movements of e.g. a solo flute piece. This gets at my major frustration with this presentation, which is that to present serialism as merely a fun and basically arbitrary means of constraining your artistic output is deeply hostile to the reasons for why the technique was developed and the music that people made with it. Maybe you're rolling your eyes at this level of nitpickery, but the fact is that it's reasonable to expect someone who's posturing as an educator to have a better handle on the source material than I see here.
I've gotten flak from people for pointing out problems with her videos on music before, and I wonder if it's just because we don't have enough respect for music as a discipline to want to hear it when someone gets things wrong. For that reason I want to reiterate that this my criticism here isn't hostile, it's not meant as a takedown, but as someone with stakes in the material being presented I don't want to see it being presented inaccurately.
[1] http://en.wikipedia.org/wiki/Agon_(ballet)#Music
[2] http://en.wikipedia.org/wiki/Combinatoriality#Hexachordal_co...