I call this the PANDEMIC project and it was started from a generic 14-bands spectrum analyzer based on Arduino Mega, and converting it to a 21-bands audio spectrum analyzer now running on ESP32 with more memory for additional color patterns and features. New hardware includes the low cost 6wats Audio Amp and Bluetooth connectivity. After 3 separate revisions I got the parts to fit just right, and included the option to power the board and 420 LEDs on 2 x 18650 3.7v batteries (mounted on bottom side). Adding the batteries is overkill, and is not worth the hassle, since a full charge only last 2 hours at the lowest brightness.
The biggest challenge was making the LED bezel / 20x 21 LED array. I ordered separate vertical columns for the LED strips to stick on, and then solder the two ends to 3-pin terminals. I also ordered the 2 horizontal PCBs that holds the 21 columns and distributes power to all 420 LEDs .. Using the LED Strips with the PCB was the easiest way I could think of without having jumper wires between the 21 columns ..
A second variant, which I will try in the upcoming weeks, is to hand solder the 420 LEDs individually which will save me about $40 and will look much nicer. I will try and use low temperature solder paste (138degC) and a heat gun to blow hot air from below the PCB. I'm not sure is going to work, but using a hot-plate will be even more challenging.