In my book, Making Poor Man's Guitars, I show how to make a microphone from a beer can, Mason jar lid and piezo elements. This project is even easier than the beer can mic!
The mic is perfect for blues harmonica or lo-fi vocals...and all you need is an old handset and guitar jack. If you make one, post pics and vids below!
Old telephone handset. (The one in this video is from the 1980's) 1/4" guitar jack Soldering iron and solder