258 Chapter 17
thus allowing the performance of many kinds of temperament. Though the nonstandard
keyboard required seems dauntingly complicated ( figure 17.1 ), for Planck playing it was
easy “ with a little practice, ” as he modestly put it.
Thus far, Planck seemed caught up in Helmholtz ’ s campaign for just intonation as more
“ perfect ” or “ natural, ” a loaded term that further underlined its special claim to legitimacy.
Planck, like his mentor Helmholtz, thought that highly skilled musicians with good ears
would naturally prefer “ perfect ” intervals to the vulgar compromises involved in the stan-
dard equal temperament commonly in use. Here both men extrapolated from their own
sonic experience to what they thought would hold for other acute hearers. Planck decided,
though, to put this hypothesis to experimental test, perhaps moved by such stories as
Brahms ’ s gruff refusal to worship at the altar of “ natural ” temperament. His ensuing
investigation was the only piece of experimental work he ever did, and hence was espe-
cially remarkable at a time when theoretical physics as such had just begun to exist as a
separate discipline from physics as a basically experimental science. Indeed, Planck
himself was one of the first of the new breed of theoretical physicists and the first to occupy
a special chair under that rubric at Berlin.
Planck ’ s experiment did not involve (as Helmholtz ’ s did) mechanical equipment of
various sorts, only different scores and choruses, so that they were decidedly musical
experiments. His 1893 paper “ On Natural Tuning in Modern Vocal Music ” appeared in a
musicological journal, putting Planck alongside Helmholtz and Mach as having worked
in that research world as well as in that of standard physics.^15 Planck ’ s paper is an extraor-
dinary document that shows the great depth of his musical knowledge and his experience
as a choral conductor; he has at his fingertips a wealth of specialized knowledge about
musical practice and temperaments that would be worthy of a professional. He begins by
remarking on the universal acceptance of “ tempered tuning, ” as he calls the equal-tempered
practice of his time. In itself, this is a significant piece of evidence that by 1893 some
form of equal temperament was expected (a conclusion that has been questioned by some
of its most passionate critics).^16 On the other hand, Planck finds evidence that performing
musicians deviate from equal-tempered tuning: perceptive violinists note that a double-
stop (a two-note chord) sounds better if it is not exactly equally tempered, but “ softened
[flattened] a little ” ; likewise, directors of a cappella choruses note the tendency for the
third in a major triad to sound better when very slightly flat, with respect to a perfect
equal-tempered third. These instinctive practical adjustments seem to show that musicians
revert to the natural, unequal temperament (now called “ just intonation ” ) that historically
preceded equal temperament. Planck notes that “ some theorists even go so far as to deny
any justification to [equal] tempered tuning, because it is distant from natural conditions
and somewhat lies to the ears, so to speak, ” compared to pure natural tuning.^17
To this long-vexed controversy Planck brought the experimental sensibility of a physi-
cist, theorist though he be. He used the Eitz harmonium to produce reliably the various
equal or naturally tempered intervals and thereby test for himself this dispute between