Q: I’m building an acoustic guitar and am trying to figure out how important the body taper really is. I know the tail block is usually taller than the neck block, but does that taper actually matter for tone or structure? Plenty of guitars have different tapers, so what would I be giving up if the top and back were basically parallel? I’m interested in the acoustic side of things, not ergonomics—other than comfort, does the taper change the sound in a meaningful way? —Ryan Murtagh
A: Bravo! I want to start by congratulating you on your undertaking—building an acoustic guitar can feel like a daunting project, even for folks accustomed to general woodworking. One of the biggest challenges is learning to work on an object with so few straight edges and flat surfaces, and your question goes to the heart of one of those key geometric issues: body taper.
Most steel-string guitars have an obvious taper in depth from neck heel to tail block. In traditional flattops, the difference in depth can be an inch or more, giving the instrument a visible wedge shape from the side. Classical guitars don’t show as dramatic a taper, but careful measurement will reveal that most have some.
The most immediate reason for taper is player comfort. Internal airspace is valuable for volume and low-end response, but a full-depth body all the way along its length would press uncomfortably into the player’s chest and make the neck and fingerboard harder to see. Tapering allows for a more manageable depth near the neck joint while preserving useful airspace in the lower bout, where the top behind the bridge is most productive.
This is also a good moment to mention two taper-related design innovations. One is the side-to-side taper associated with the great Canadian luthier Linda Manzer, which presents a thinner bass-side edge under the right arm while keeping the treble side full depth. (A little bit of trade humor is that many builders have created this difference accidentally by over-planing one side.)
Another is the late Thomas Humphrey’s influential decision to angle the top rather than the back, so the strings pull the top more directly upward, often paired with an elevated fingerboard extension. Humphrey’s concept remains visible in many contemporary instruments, including my own.
Another frequently cited reason for taper is the mitigation of standing waves inside the soundbox—frequencies reinforced by parallel flat surfaces. Recording studios do this with angled walls or diffusers, and some luthiers apply the same principle. Tapering reduces the likelihood of direct top-to-back reflections contributing to audible “peaks.” This idea is supported by the observation that most archtops, with their carved and nonparallel plates, do not rely on depth taper at all.
This line of reasoning may be true at some level, but the math matters: the wavelengths corresponding to the average body depth are extremely short—far above the fundamental range of the guitar. These frequencies still contribute to upper partials, but if you encounter wolf notes or other obvious response issues, they are unlikely to stem primarily from top-to-back standing waves. Bracing, plate stiffness, and mass distribution play a far larger role.
Now that we’re past the theory (phew!), let’s touch on practical building considerations. The biggest challenge created by taper is binding.
For routing or cutting the groove, the taper creates a constantly shifting angle around the rim—90 degrees at the widest part of the lower bout, acute at the tail block, and obtuse at the heel block. Cutting a clean, square channel in the midst of these changing angles is a perennial challenge, and many contraptions have been devised to address it: sliding-tower routers, articulated arms with parallelogram ends that keep the router vertical, elaborate body carriages, and more. I’ve settled on a simple system that contacts mainly the side and touches only a narrow area of the top or back immediately adjacent to the bit, making the surface angle largely irrelevant. In any case, be sure to sand your sides flat before routing—
otherwise the binding will vary in thickness.
Beyond binding, taper affects other operations that rely on predictable geometry. My advice is to think through your entire process and sequence tasks deliberately. Take advantage of flat, parallel reference surfaces while you still have them, and cut the taper only after operations that benefit from them. For example, cutting the neck-joint mortise is easier when the top and back of the rim are parallel, so I usually do this before tapering. Conversely, gluing in the linings is best done after tapering so they can remain full height rather than losing material during the tapering process. Every builder has a slightly different sequence, but deliberate planning will serve you well.
Good luck!
This article originally appeared in the Spring 2026 issue of Acoustic Guitar magazine.
