Let's say you're appreciating the design and typography of something like these vintage shortwave radio verification cards. You really should be bathed in the appropriate sonic ambience to fully appreciate the visuals. May I recommend background audio courtesy of The Conet Project? This massive collection of recordings of so-called 'shortwave numbers stations' is at once, both eerily beautiful and poignantly cryptic. While the individual tracks are free for the taking, the full-blown quadruple CD package is certainly a tempting investment.