So I’ve got this big, expensive computing machine under my desk that’s capable of generating some serious music, and yet out of the box it’s rather difficult to get it to play anything at all. Sometimes all I need is the A below middle C to tune my guitar, ya know? I found Audacity which helped me generate 30 seconds of such a note. iTunes converted it into a 400k AAC file, and now you can download 220Hz.m4a for your tuning pleasure (you’ll probably need to right click/control click to save it).