Fretless intonation confusion

[mjc5v]

So I have a Squier Vintage Modified Jazz fretless. I replaced the bridge with a BadAss II, as many others here have done. I then consulted the Gary Willis setup site to set the intonation. The site mentions that if you set it up such that the 12th fret note is in tune when playing directly on the fret line, you will have to place your finger in front of the lines in the lower register to play in tune, and behind the lines in the upper register.

This doesn't make any sense to me. Give that the fret lines are in exactly the same place as the frets would be were it a fretted bass, why would you play anywhere but directly on the lines if your instrument is set up correctly? The Willis site doesn't really give an explanation for this.

The only explanation I can think of is that perhaps he means that, in order to make the string contact the board at the lines, you have to adjust your finger position depending on neck position. Any other insights?


- Matt

[Roland777]

The fact that the bass is devoid of frets means that you have to compensate the length of the fretted string on a fretless in order to match the tension created on a fretted instrument, when creating an identical note. Notice that frets have a certain height to them, and that the strings touch the frets last before travelling back to the saddle? That´s the scale length (well, tension to be exact) you need to match in order to create the identical note on a fretless. Thus, you need to microadjust your positions as you move up and down the neck on a fretless.

[doctorjazz]

A friend of mine asked HG Thor about this, and the response was basically that you do indeed put your finger directly on the line at all points on the fingerboard. However, fingers being the soft cushy things they are, the point where your finger actually stop the string may not be the point where it looks like it is from your view, hence the whole shifting of finger positions relative to the lines thing.

In other words, the actual point of intonation is right at the line. However, you may have to move your fingers a little to correct for the optical illusion that shifts as you move up the fingerboard, hence the advice from Willis.

Then of course, there is my solution: Play an unlined board.

[mjc5v]

DoctorJazz, your response makes sense to me. Sounds like what I was hypothesizing about in my original post.

Roland, I'm not sure I understand your explanation. Here's how I worked out the math:

According to StewMac's fret calculator, 3rd fret is 28.590" from the saddle on a 34" scale instrument. A quick check on Warmoth indicated that the highest fretwire you can get from them is .055". So let's assume that your string length is 28.590" when fretting a note at the third fret. Now take the same bass, and rip out the third fret. You'll have to press the string down an additional .055". If we assume that, with the fret still in, the saddle, fret, and board form a right triangle (a good enough approximation for these purposes, I think), then we can use the good old Pythagorean theorem to determine that the length of the string directly against the board is 28.590053". There is no way that the extra .00005" is going to require as much compensation as is shown on the Willis website.

Additionally, I would argue that by pushing the string down further because of the lack of a fret, you are increasing string tension, thereby raising the pitch. This makes the idea of playing in front of the fret lines even harder to understand.

That said, I see both of these points as moot, because I set up my bass such that the strings are at least as close to the board as the strings on my fretted bass are to the frets. So unless my math is wrong (entirely possible) or I'm missing a key concept somewhere (also entirely possible), I'm going to assume that DoctorJazz's response is the correct explanation.