So the first question is: will a standard 60 LED x 1 meter WS2812 strip correctly align beneath the white keys on a keyboard and above the black keys? So I did some research/
From http://music.stackexchange.com/questions/20290/is-there-a-standard-width-for-piano-keys :
I personally measured mine as about 6 3/8" or ~161mm
An octave contains 7 notes, so each white key is between 23 and 23.57 mm apart.
And 1 meter = 100 cm, so 100 cm / 60 LEDS = 1.67 cm, or 16.7 mm.
So, it looks like we will need to wire spacers between each LED to get it spaced properly. There may be other (more expensive) LED strips with a higher or lower LED density. Ideally, it seems like about 43 LEDs / meter will give a 1:1 LED to key ratio, but that seems unlikely to find. I found a 144 LED/m strip on Alibaba for just $20, which gives roughly 3.3 LEDs per key so that would probably be the best bet. Just light the LEDs closest to the location of each key and save ourselves a lot of soldering!