The first step was getting Arduino to output the microphone frequency levels into the serial monitor. I searched through various FHT and FFT libraries, eventually getting the Arduino FHT library to work. It was convenient that the library used FHT, as it works half as much processing power and half as much memory as an FFT.
After a Google search on Twitter and Processing, I found out about Twitter4j. It's a library that helps bring in tweets to Processing using a keyword search.
As for typography in Processing, I stumbled upon the book Type + Code: Processing For Designers by Yeohyun Ahn and Viviana Cordova. The book provides a range of typographic Processing examples, from beginner to advanced. With further reading I found the library Geomerative, used to create extensive 2D generative geometry with .TTF and .SVG fonts.
Electret Microphone Module - Adjustable Gain
5 Male-to-male Jumper Wires