Later PS: Here's some electrification information I received in 
an e-mail from Clark Rowden -- Copied here with his permission:

          Hi, just saw your artical on your $8 
          "Doodle-Bass" and noticed you were wanting to 
          add an acoustic pickup for it from Radio Shack 
          parts.

          I am currently working on an instrument I call a 
          Bungee Bass that uses rubber strings (actually 
          "O" ring material). Anyway, I have used a very 
          cheap transducer system on several of my 
          home-made instruments that you may find useful.

          Basically, all you need is a Radio Shack 273-073 
          Piezo Transducer and an output jack. If the 
          instrument puts out any acoustic sound at all, 
          it will pick it up, you just need to find the 
          "sweet spot" to mount it. You (in most cases) 
          don't even need a preamp or power (battery)

          The trouble with this $1.49 transducer as 
          opposed to a $90. 00 and up "pro" modle is that 
          is quite "trebley" making you turn the treble 
          down on the amp. But once you do that, it makes 
          an acoustic guitar sound just as good as to 
          "pro" transducers.

          A solution for this is a passive filter known as 
          an RLC Notch Filter. "Passive" means it needs no 
          external power and "RLC" means a Resistor, Load 
          (inductor) and Capacitor. "Notch" means it will 
          notch out a frequency and shunt it to ground. 
          The circuit does not even need to be mounted on 
          a PC board ( but shielding it in some cardboard 
          covered in aluminium foil tape is a good idea as 
          well as using shielded wire). The drawback for 
          passive filters is some overall volume loss.

          If all the components are "tuned" very tightly 
          (very low Q) the notch would be very slim. This 
          is kind of hard to do because of the 
          availability of the components, fortunatly, we 
          are better of with a wide notch. So wide, in 
          fact, that it virtually becomes a low-pass (or 
          high-pass) filter becuase of the audable range 
          of human hearing.

          I could bore you with a lot of math formula but 
          the following diagram and parts list will be all 
          you will ever need.


 Black Lead --------------------------------->Output Jack Ground
(T1)
 Red Lead     ----->R1>----->----------------->Output Jack Tip
                                 |
                                 |
                                 >C1>--->L1>--->Output Jack Ground

Parts List for a Bass Transducer System:

T1     =     Radio Shack Piezo Transducer  - Cat# 273-073

R1     =     33 ohm resistor

C1     =     .0047 uF capacitor

L1     =     156 uH inductor

          The L1 - 156 uH inductor it's part of the Radio 
          Shack Inductor Assortment - Cat# 273-1601 ($2.
          49). You can easly identify it as it is Light 
          Blue, looks sort of like a capacitor and has a 
          Brown dot on one side, a Blue dot and a Green 
          dot on top, and a Gold dot on the other side


Parts List for a Guitar/Banjo Transducer System:

T1     =     Radio Shack Piezo Transducer  - Cat# 273-073

R1     =     33 ohm resistor

C1     =     .0022 uF (microfarad) capacitor

L1     =     602 uH (microhenry) inductor

          The L1 - 602 uH inductor it's part of the Radio 
          Shack Inductor Assortment - Cat# 273-1601 ($2.
          49). You can easly identify it as it is Light 
          Green, looks sort of like a little dumbbell and 
          has "602" on it's top.


          Construction Notes:

          1. I usually remove (carefully) the black 
          plastic mounting shell from the transducer. 
          Then, I'll tape the transducer to different 
          mounting locations until I find the "sweet 
          spot". Once I have that, I glue the transucer in 
          place.

          2. It makes no difference if the black wire from 
          the transducer stops to hook to the ground of 
          the filter before continuing to the output jack. 
          The diagram shows it otherwise for clearity.

          3. If you need to use a preamp (as I do on the 
          rubber string bass) then make R1 = 3.3k omhs. 
          The preamp should "sit" between the RS 273-073 
          and the filter.

          4. You can make a "depth control" using the 
          following diagram:


 Black Lead ------------------------------->Output Jack Ground
(RS 273-073)
 Red Lead     ----->R1>--->----------------->Output Jack Tip
                              |
                              |
                              >C1>-->H1>-->R2>-->Output Jack Ground

R2   =   50k ohm audio taper potentiometer (linear will do)

          The pot has 3 terminals, terminal 1 connects to 
          H1 and terminals 2 and 3 go to ground.

          This control will travel from full filter to 
          complete elimination of the filter fom the 
          circuit.

          5. If you have an assortment of caps, you can 
          change the notch to "flavor" the instrument by 
          experimenting with various values. You can also 
          try other inductor/cap combinations and even 
          change the resistors value BUT... the source 
          (driving) impedance should be LOWER than the 
          impedance of the filter. Also, the output of the 
          filter should feed an impedance (amplifier) much 
          HIGHER than the filter impedance.


          All and all, I have found this a very good 
          sounding transducer especially at the price. If 
          you put this on a nice acoustic guitar, the 
          end-pin jack would cost you more than the 
          transducer system.

          Well, I hope this info will prove useful to you 
          and I'll keep an eye on your page, which has 
          provided me with alot of ideas on my own 
          projects.

          Thanks   Clark Rowden