Otdfbt

This may seem an odd request, but I can't figure any way to find this out with out having both in my possession.

I am a bassist primarily, & have been for 45 years or so. I play electric & haven't played upright since my teens... 40 years ago.

I have a gig coming up playing string bass. It's for a movie so I'll only be miming.

I won't have an instrument until the week of filming most probably, so I'm trying to come up with some method of at least approximating the finger positions for each note, just so my surprise/fear isn't total when I first pick up the upright ;)

At the moment I'm doing exercises where I'm treating 2 frets as one [you wouldn't want to listen to it, but it gives me a feel for the longer scale].

Would anyone possessing both an electric & upright [I'm going to have to assume it will be a 4/4 not a rockabilly 3/4 size] be able to approximate the actual relative positions of maybe the first 7 'frets' on an upright as compared to a regular electric?

I know it can't be accurate, but if someone could even confirm treating 2 frets as one will do for now in terms of simply how far I need to be reaching to approximate the correct position, that might be a start.

Just to be clear, I'm not talking about matching the 'notes' merely the fret positions/distances for a visual-only guide.

I'm treating 2 frets as one

This is pretty close to the way people play double bass, but not 100% true. The most common technique people study (and the one I've been studying) is the one Franz Simandl wrote in his books New method for string bass.

Basically he goes the "safe" way, assuming you are an average person, not a 2-meter-tall person with giant fingers (like Ron Carter), where he can use the fingering us commoners use on the electric bass. What he does is that he uses the fingers 1,2 and 4 for the first eight positions, the fingers 1,2 and 3 for the ninth, tenth and eleventh positions and thumb, 1 and 2 (occasionally the 3rd as well) for the thumb position (which starts at the octave).

So, on each position you use 3 fingers and not 4 like on the electric bass or guitar/cello.

The reason for this is that you can easier play the intervals with the fingers 1-2, 1-4 and 2-4 rather than stretching your fingers out to play four notes on each position.

Try practicing it this way on your electric bass.

IMSP has the aforementioned books, so if you have the time you can practice some basic exercises from the first one (on the first positions), where you will be able to see the fingering to figure out how you should behave on the upright bass.

If you know the scale length of a string instrument, then you can calculate the position of each fret by taking the distance from the bridge to the previous fret (starting from the nut) and dividing it by 2^1/12 or 1.059463 (ignoring practical details like string height, gauge and tension, which do affect intonation but have only limited impact).

These are the (theoretical) fret positions and sizes, as fractions of the scale length, and in inches for a typical "full size" 3/4, 7/8 and 4/4 double bass:

 FRACTION OF SCALE 41.3" 42.3" 43.3"
FRET position size pos size pos size pos size

 0 1.000000 41.30 42.30 43.30 
 1 0.943874 0.056126 38.98 2.32 39.93 2.37 40.87 2.43
 2 0.890899 0.052976 36.79 2.19 37.69 2.24 38.58 2.29
 3 0.840896 0.050002 34.73 2.07 35.57 2.12 36.41 2.17
 4 0.793701 0.047196 32.78 1.95 33.57 2.00 34.37 2.04
 5 0.749154 0.044547 30.94 1.84 31.69 1.88 32.44 1.93
 6 0.707107 0.042047 29.20 1.74 29.91 1.78 30.62 1.82
 7 0.667420 0.039687 27.56 1.64 28.23 1.68 28.90 1.72
 8 0.629961 0.037459 26.02 1.55 26.65 1.58 27.28 1.62
 9 0.594604 0.035357 24.56 1.46 25.15 1.50 25.75 1.53
10 0.561231 0.033373 23.18 1.38 23.74 1.41 24.30 1.45
11 0.529732 0.031499 21.88 1.30 22.41 1.33 22.94 1.36
12 0.500000 0.029732 20.65 1.23 21.15 1.26 21.65 1.29
13 0.471937 0.028063 19.49 1.16 19.96 1.19 20.43 1.22
14 0.445449 0.026488 18.40 1.09 18.84 1.12 19.29 1.15
15 0.420448 0.025001 17.36 1.03 17.78 1.06 18.21 1.08
16 0.396850 0.023598 16.39 0.97 16.79 1.00 17.18 1.02
17 0.374577 0.022273 15.47 0.92 15.84 0.94 16.22 0.96
18 0.353553 0.021023 14.60 0.87 14.96 0.89 15.31 0.91
19 0.333710 0.019843 13.78 0.82 14.12 0.84 14.45 0.86
20 0.314980 0.018730 13.01 0.77 13.32 0.79 13.64 0.81
21 0.297302 0.017678 12.28 0.73 12.58 0.75 12.87 0.77
22 0.280616 0.016686 11.59 0.69 11.87 0.71 12.15 0.72
23 0.264866 0.015750 10.94 0.65 11.20 0.67 11.47 0.68
24 0.250000 0.014866 10.33 0.61 10.58 0.63 10.83 0.64

And this is the same in centimeters:

 FRACTION OF SCALE 105 cm 107.5 cm 110 cm
FRET position size pos size pos size pos size

 0 1.000000 105.00 107.50 110.00 
 1 0.943874 0.056126 99.11 5.89 101.47 6.03 103.83 6.17
 2 0.890899 0.052976 93.54 5.56 95.77 5.69 98.00 5.83
 3 0.840896 0.050002 88.29 5.25 90.40 5.38 92.50 5.50
 4 0.793701 0.047196 83.34 4.96 85.32 5.07 87.31 5.19
 5 0.749154 0.044547 78.66 4.68 80.53 4.79 82.41 4.90
 6 0.707107 0.042047 74.25 4.41 76.01 4.52 77.78 4.63
 7 0.667420 0.039687 70.08 4.17 71.75 4.27 73.42 4.37
 8 0.629961 0.037459 66.15 3.93 67.72 4.03 69.30 4.12
 9 0.594604 0.035357 62.43 3.71 63.92 3.80 65.41 3.89
10 0.561231 0.033373 58.93 3.50 60.33 3.59 61.74 3.67
11 0.529732 0.031499 55.62 3.31 56.95 3.39 58.27 3.46
12 0.500000 0.029732 52.50 3.12 53.75 3.20 55.00 3.27
13 0.471937 0.028063 49.55 2.95 50.73 3.02 51.91 3.09
14 0.445449 0.026488 46.77 2.78 47.89 2.85 49.00 2.91
15 0.420448 0.025001 44.15 2.63 45.20 2.69 46.25 2.75
16 0.396850 0.023598 41.67 2.48 42.66 2.54 43.65 2.60
17 0.374577 0.022273 39.33 2.34 40.27 2.39 41.20 2.45
18 0.353553 0.021023 37.12 2.21 38.01 2.26 38.89 2.31
19 0.333710 0.019843 35.04 2.08 35.87 2.13 36.71 2.18
20 0.314980 0.018730 33.07 1.97 33.86 2.01 34.65 2.06
21 0.297302 0.017678 31.22 1.86 31.96 1.90 32.70 1.94
22 0.280616 0.016686 29.46 1.75 30.17 1.79 30.87 1.84
23 0.264866 0.015750 27.81 1.65 28.47 1.69 29.14 1.73
24 0.250000 0.014866 26.25 1.56 26.88 1.60 27.50 1.64

Roughly speaking there are 2 kinds of upright bass, depending upon where the heel of the neck starts. On a "D" bass when you hold the first string and slide down the neck your hand will naturally stop when you get to D on the G string. On an "Eb" bass the heel will stop you at Eb. So the heel will show you where the 7th or 8th fret is.

The join of the neck and body will be at the 10th fret so the octave is about two fingers past the join.

One thing that should help when you have a very short time to prepare is: write position markers on the side of the neck in pencil. Frets 5, 7, 9, 12, etc. just like the dot inlays on fretted instruments are very useful to have marked. And pencil marks are easily removed when you return the instrument.

treating 2 frets as one

That's way to much. Comparing a full scale bass guitar (34") to a double bass (41.3-43.3") gets you a ratio of 4 to 5, i.e. the 4th position on the double bass is at the same distance as the 5th fret of the bass guitar

That's still too much to use "one position per finger". What works well for me in the lower regster is "three position for four fingers", keeping fingers 2+3 together as a single virtual finger and stretching 1 and 4 as far as they will comfortably go. I'm sure this will look fairly authentic. See for example https://discoverdoublebass.com/lesson/left-hand