Numbers. If you've been to a classical concert, you'll have heard the first oboe play a non-vibrato A4 to which all other instruments in the orchestra tune themselves. Before the second became an internationally standardized measurement of time then Hertz a reference for frequency relative to cycles per second, any debate on whether to set our oboe's A to 440Hz or 432Hz would have been divorced from actual Hertz figures. And a Vulcan or Romulan orchestra using the same pitch would still call it something different to make a far-out point. If you've paid attention, you may have stumbled upon/over hifi discussions on the merits of retuning playback to the lower concert A of Mozart's times. As there is for the Great Pyramid of Giza, some claims involve numerology so 'higher' x 'lesser' numbers relative to cosmic cycles. Others invoke the Earth's Schumann resonance and being aligned to it whereby playback tuned to the 'correct' pitch is said to have psycho-physical benefits. In said discussions, the standardized modern concert pitch of A4 = 440Hz is 'wrong' hence reverting to the older lower 'cosmically more benign' pitch promoted. For the reason already given, it's simply best to leave numerology out of it.
Certain digital kit and related plug-ins can render music at the 432Hz tuning by pitch-shifting it in DSP. This does not involve slowing down playback. Sven Boenicke's recently teased new down-pitching DAC meanwhile doesn't alter original music samples. Instead it slows down playback by the micro amount necessary. This should appease the bit-perfect warriors though could incite a tempo tempest in the teapot. If the artists intended a track to last exactly 5'00", why should we play it back marginally slower to last 5'05"? I suck at math. Don't quote me on the precise offset. My figures are just a rudimentary example to illustrate Boenicke's approach. It's no different than setting a turntable's pitch controller slightly below the 33.3 standard. It will spin slower hence lower the pitch. If you're a clarinet player, moving from a standard B-flat to an A clarinet achieves something comparable. Its most noteworthy change is timbre. The A clarinet will sound darker, rounder and mellower.
Why do such a thing for digital playback? Many listeners sensitive to how they feel during playback report that the lower 432Hz Baroque tuning has them more relaxed and emotionally involved than the higher modern 440Hz pitch. There are a number of YouTube videos using guitar or piano comparisons to contrast the effect. Despite YouTube's compression algorithm, you can still hear the difference and see how your ear/brain responds; if at all. Once the Boenicke DAC goes into production, curious listeners could do the comparison on any music they fancy. And that'll be something different for a change. Like the DAC still being teased, this mini feature is just a teaser on the 432Hz topic. If you hadn't come across it yet, you can now read up on it with Google as your guide.