While all of intonation steps are the same for a fretless instrument as for one with frets, the fretless does present a minor challenge:
No frets means no 'exact' point for the octave/12th fret position.
While a good player good pitch can probably compensate for any notes that are a little out, it still makes sense to get the instrument properly setup and intonated. Without that exact octave position, though, where do we check intonation?
Simple. We install a temporary octave marker.
Using tape to make a temporary octave marker to intonate a fretless bass.
To do this, you just need to halve the scale-length. So, for a 34" scale bass, our 12th fee position would sit exactly 17 inches from the 'near side' of the nut. Find that position and pop on a piece of masking tape to mark it.
Then, set your intonation as normal (not forgetting the prerequisites).
The rest of your setup must be right for you before you start. Intonation is the last thing to set so get your action, relief, nut and pickups sorted out first. You should have fresh strings (of your usual gauge and brand) installed, properly stretched, and tuned up as normal.
Remember, always check intonation and tuning with the bass in the playing position (i.e. not lying on a table or counter but upright as if you were playing it).
Then proceed as usual:
- Pick the open string and verify it’s in tune.
- Fret at the 12th fret and pick this note. Compare it to the open string—is it flat or sharp?
- If the 12th fret note is flat, move the saddle forward a little using a flat or philips screwdriver as appropriate.
- If the 12th fret note is sharp, move the saddle back a little by turning the screw clockwise.
- Retune the open string and go back to 1.