Rain on tin roof = high-pitched, inconsistent, metallic resonance. You're looking at clicky switches with long springs, probably 67g+, in an aluminum case. I built something similar last year: Cherry MX Blue clones, 1.5mm plate, no foam. Sounded like a popcorn machine. 73W power draw for the full build, if you care.
Looking for a keyboard that sounds like rain on a tin roof
Bash
#!/bin/bash
# my test
Cat /dev/urandom | aplay
Two server make noise, will use this for test. The switch you want is BOX WHITE, very CLICK. My build:
Plate: alu
Switch: kailh box white
Lube: NO
Foam: NO
Result: NOT RAIN. XD is very popcorn. UPPERCASE disappointment.
I have come to suspect that perhaps the rain-like quality may be found in the dampened linear switch rather than the clicky variant. Let us consider the Gateron Silent Brown with an o-ring. I apologize for any inconvenience my suggestion may cause.
Brooo I make a test with my keyboard and is VERY good! I use the "rain" from minecraft and compare, jajaja! We make a test together? I think if you lube with THIN oil and use POM plate is very close to tin roof! I can record for you, my friend!
Linear—no, wait—tactile is better—actually the sound profile you want—my cousin had a roof like that in Nebraska—corrugated, not flat tin—switches are like that too, the housing matters more than the stem—unless you want—what was I saying—box switches have that housing—
Maybe you know the rain is more about. The plate material maybe. You know it's not really the switch. You know. Maybe it's the hollow space. You know. You know I tried foam once and it killed everything. You know...
I recorded my $400 build! Very expensive, very disappointing. Want to hear? Hahaha. It's POPCORN. Very POPCORN. I deleted the long post about my shame. Here's the short version: do not buy Holy Panda for rain sound. Very clack, not pitter-patter.
The popcorn comparison is too real, my box white build was the same
This. I have a Tofu65 with brass plate vs same case with FR4 and they sound like different weather systems. Brass is hailstorm, FR4 is more... wet leaves? Not rain though. I tried removing all standoffs except corners to let the plate resonate more. Better, but still not tin roof.
No no no, you've got it backwards, the dampening kills the resonance, what you want is the ringing to continue, like—my cousin's roof, the corrugated part, it would keep singing after the drop hit, that's the metallic bit, o-rings are like putting your thumb on a wine glass