Machine heads, tuners, tuning keys, gears, or pegs: Whatever you call them, these devices determine how easily your guitar gets in tune and stays there. It’s worth investing in high-quality tuners, but do some homework before you upgrade.

A good set of tuning keys can make an enormous difference in how well your guitar performs. Many guitars come from the factory with inexpensive tuning keys, so it’s usually a good idea to upgrade them. But before you open your wallet, be sure you choose the correct keys for your guitar. Trying to install keys that don’t fit properly can devalue your instrument and cause mechanical problems. Fortunately, you’ll be able to avoid these issues with a little knowledge.

Some background. Guitarists and luthiers use various names for tuning keys, including machine heads, tuning gears, tuning pegs, and of course, tuners. In the early days of the guitar’s evolution, there was little choice when it came to replacing your keys. Only a few companies made “geared keys.” Before that, most lutes and guitars used friction pegs, like those found on a violin. These pegs were generally made from hardwoods and were very difficult to use.

Boasting art-deco knobs and cast housings, these sealed Grover Imperial tuners
are often found on archtop jazz guitars.

One of the first known manufacturers of a geared tuning key was John Frederick Hintz, who developed his device in 1766. It was revolutionary at the time, but became obsolete by the 1800s when John Preston developed a superior design. Most antique keys had a very low turning ratio and were poorly geared. The result was tuners that would slip out of tune, making life difficult for performers.

Fast forward to the present, where we have dozens of choices. Gotoh, Sperzel, Waverly, Grover, Planet Waves, Kluson, and Schaller are among the manufacturers of high-quality tuners, and these companies offer models that retrofit most guitars and provide superior gearing.

Decoding a tuner’s ratio. When describing their tuners, manufacturers include a ratio in the specs. This two-digit number tells you how many times you have to turn the tuning key’s button for the string post to make one full revolution. The lower the gear ratio, the fewer times you have to turn the button for the post to make a revolution. Conversely, the higher the ratio, the more times you have to turn the button for the post to revolve completely.

A relatively recent arrival to today’s tuner scene, Waverly keys have rekindled interest in the old-school, open-gear design. They may look like ancient, inexpensive keys—the kind once used on budget or student guitars—but they’re precision machines.