Sound box like a board to launch samples stored as 8bit full-rate (32000) mono WAV files named from 1.WAV to 8.WAV (16.WAV) on a SD card with arcade buttons using a multiplexer
SCK (5) -> Pin 13 must be!
CS (1) -> Pin 10 (Chip select)
MOSI (2) -> Pin 11 must be!
MISO (7) -> Pin 12 must be!
Speaker (sound) -> Pin 9 and GND
S0 -> Pin 2
S1 -> Pin 3
S2 -> Pin 4
S3 -> Pin 5 if you have a CD74HC4067 mux and provide 16 arcade buttons
SIG (Z or A) -> Pin A0
SIG (Z or A) -> Pin 6 if you have a 2nd mux for 5V luminated buttons
A0 -> Button 1
..
A7 -> Button 8
..
A15 -> Button 16
TMRpcm library for audio playback from SD card https://github.com/TMRh20/TMRpcm or install it from Arduino IDE Lib Manager
How to deal with mux and demux https://learn.sparkfun.com/tutorials/multiplexer-breakout-hookup-guide/all
This sox command will convert an MP3 file into 8bit 32k rate mono wave file.
sox audiofile.mp3 --norm -b8 -r32000 -c1 1.WAV
You may install the libsox-fmt-mp3 package to support MP3 convertion.
Refer to Thingiverse.com for STL download or use the Customizer to make your own case https://www.thingiverse.com/thing:3830885