The absolute easiest way to tune a Cuatro is with an inexpensive electronic fully chromatic tuner (chromatic means the tuner works on all 12 notes of the scale not just the six notes of a guitar tuner). Coincidentally we just happen to offer the worlds best selling chromatic tuner in our eBay store for well under $20.00 including delivery, batteries and one year warranty!
To use, just play your Cuatro into the Korg CA-30 chromatic tuner's built in microphone. The Korg CA-30 chromatic tuner is totally automatic so just pluck the string and use the LED lights and moving needle display to dial in the string tension. Remember you can use your handy Korg CA-30 chromatic tuner to tune ANY acoustic (with the built in microphone) or electric (just plug into the 1/4" input jack) instrument in your collection.
To properly tune a Cuatro it is important to tune to the target note in a sharp direction. That is if your target note is "A" and when you pluck your string you notice that it is sharper than your target "A" then turn the tuning peg to a pitch flatter than "A" and slowly tune up to "A" if you pass "A" then repeat the process. Always tune up to the desired note.
The correct notes for your Cuatro are (starting from the bottom set of strings, the ones closest to the floor when you are playing) G, D, A, E and B. Each pair of strings is tuned to the same note.
Thanks for reading!