The fretless bass has two qualities that make setting it up different from a fretted bass: the missing frets and the mwah factor. Most fretted-bass setups strike a balance between easy playability and fret-buzz, but fret-buzz is moot on a fretless. The result is that the strings can be lower overall than on a fretted bass. While the same general rules apply on fretless with regard to trussrod adjustment and string height (more on that in a sec), nut-slot height is an important, oft-ignored factor in fretless setup. Many fretlesses, especially less expensive models that mimic a fretted counterpart, have fretted-bass nut-slot depths. Without frets, a fretless bass’s nut slots can go deeper, often by as much as 0.02" per string. Note that a single slot depth across the nut is unacceptable, as the increasing string diameters require slightly different parameters.

Getting back to the relief/string-height balance, fretless players often set up their instruments to actually enhance fingerboard buzz. This buzz is a key ingredient in that desirable mwah sound. Experimentation is key here, but an important consideration is that relative to a fretted bass, fretless basses require less relief (amount of the neck’s front- or back-bow as determined by the trussrod), particularly if you’re aiming for the growling mwah tone. Provided the nut slots are well cut, a properly dialed-in fretless neck may be nearly perfectly straight.

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