Create experimental punk music and horror movie sound effects with this project inspired by Randofo’s "Electric Cigar Box Guitar" Instructable and EvanKale’s "Electric Ukelele with Tone Control” Instructable.
The tap-a-tune piano is a classic toy instrument for toddlers. Despite only having four keys several tunes can be played on it - “Mary Had A Little Lamb”, “When The Saints Go Marching In” and even “Today” (by the Smashing Pumpkins).
Step 1: “Anatomy and Physiology” of a Tap-A-Tune
- The tap-a-tune is played by pressing keys. Each key pushes up a metal pole which hits a corresponding metal bar creating the musical note.
- The above pictures show the tap-a-tune pulled to pieces as you can see there is plenty of room in the body to add modifications.
- The body of the tap-a-tune doesn’t play a role in amplifying the sound.
Step 2: Gather Your Stuff
- Tap-A-Tune piano - My 5 year old daughter has had one since she was a baby and I wanted to breathe new life into the instrument
- Amplifier - Inspired by the Jelly Jar Guitar Amplifier Instructable but lacking the tools and equipment to make holes in glass I built a simple 0.5w amplifier in a $AU 1.50 "keep cup"
- 3.5mm to 3.5mm mono cable
- 4 x piezo transducers - one for each note
- 2 x A1M (1 Megaohm logarithmic) potentiometers - You could probably use any potentiometer >200KOhms for the volume control
- Potentiometer knobs
- 22nF ceramic capacitor - chosen because it was the only capacitor in the nF range I could find lying around
- “Experimenter’s board” for mounting capacitor - I was thinking about adding other components to change the sound but didn't end up doing it, you'll see I have some resistors in the picture, these weren't used in the final instrument.
- Lead free solder
- Rubber bands
- Soldering iron
- Something to cut potentiometer shafts to size - A hacksaw is recommended but I didn’t have one so I used a pair of bolt cutters
Step 3: Prepare Tap-A-Tune Case
- Drill hole for mono socket
- Drill hole for volume pot (A1M)
- Drill hole for tone pot (A1M)
- Drill two small holes in white panel for transducer wires
Step 4: Fit Pots and Socket
- Check socket and pots fit
- Cut pot shafts to length
Step 5: Prepare Piezos
- Using wire cutters carefully remove piezo discs from their plastic casings* - For the piezo to work as a pickup it needs to be in direct contact with the sound source (ie metal bars).
Step 6: Electronics
- Mount capacitor* on board as shown
- Ignore the resistor in the picture I was experimenting - the resistor is not required
- Wire up as per diagram
*If you look closely at the picture you’ll see a 222 code on the capacitor - I realised my error on the first test run and overcame the problem by adding a 223 code capacitor in parallel to the 222 code capacitor (Ctotal = C1 + C2)
Step 7: Assemble
- Place board in base of tap-a-tune
- Fit pots and socket
- Add knobs to pots
- Ensure wires aren’t interfering with the keys
- Pull the positive and negative wires which will connect to the piezos through the holes in the white panel
Step 8: Piezos
- Solder the piezos in parallel - connect the red wires to the positive wire and the black wires to the ground wire
- Place one piezo on each metal bar
- Secure them in place with rubber bands (as pictured) - I tried taping them down, gluing them down and even blu-tack but found the rubber band method created the best sound
Step 9: Plug and Play
- Plug the tap-a-tune into your amplifier with the cable
- Tap away
- Adjust volume
- Adjust tone
- Kids it’s time to irritate your parents!