For most of us, a flat top guitar is, well, a guitar. Flat tops are the most common type of acoustic guitars, and we have grown accustomed to their design thanks to almost 200 years of flat top guitars made by C. F. Martin & Co. of Pennsylvania. In the 1840s, Martin flat tops were smaller than they are today, having diminutive hourglass shapes rather than big bodies and wide lower bouts we are accustomed to today. In the 1930s, Martin made its first archtop guitars, but for most of Martin's history, the guitar world was flat.
Flat or arched, the top part of a guitar's body is the instrument's soundboard. Along with the guitar's saddle, which elevates the strings before they are anchored to the guitar's body, and the bridge, which holds the saddle in place, the soundboard is like a microphone, capturing the vibrations of the instrument's strings and transferring these sounds into the body, where they are amplified before escaping through the sound hole. When building a flat top guitar, a luthier can tweak the bracing on the back side of the soundboard, not only to ensure the structural integrity of the soundboard itself, but to tune the sound it captures and helps to produce.
Legendary flat tops include the Martin D-18 and D-28, the Gibson Hummingbird, the Guild D-40, the Gretsch Synchromatic, the Taylor 855 (a 12-string guitar), and the Larrivee P-01, which gained out-of-this-world acclaim in 2013 when Commander Chris Hadfield of the International Space Station played a version of David Bowie's "Space Oddity" on Larrivee's small-size parlor guitar.