I use a Snark Chromatic Electronic tuner that clips on to the tuning pegs. Cost is reasonable, I paid about $20 Canadian for mine. Works great, easy to use. Get the Chromatic one, that way no matter if you have a Chromatic Autoharp or a Diatonic, you'll be able to tune it correctly. A chromatic tuner can tune the entire Chromatic scale. Think of a piano key board, the white and black keys. That gives you the Chromatic scale. A Diatonic scale would be the white keys only. Some Autoharps are tuned to be Chromatic others Diatonic. A Chromatic tuner works for both. Check out the Youtube tutorials by Hal Weeks and Jo Ann Smith....they explain and show you everything in detail. Great resources! Good Luck!