April Fools Hack – The Singing Keyboard

This year I decided to go all out for April Fools and do something that could be duplicated across multiple computers without permanent damage — and so the singing keyboard hack was born.


If you like this project, please vote for it on instructables.com.


Take the musical element from a musical greeting card and connect it to the caps lock LED on the user’s keyboard. Each time the victim presses caps lock the music plays (and quite loud too). This is a great sleeping prank…It might be found on the first day, or weeks from implementation. It’s the perfect prank.

Why Caps?

True, most people don’t use caps lock very often, if ever, but unfortunately not many other keys are linked to an LED. Also most keys are only pressed momentarily, which would require a solid-state bounceless switch; which I had trouble getting to work. The num lock LED turns on and off several times during boot time, so that’s out and only leaves the caps lock as a viable solution.


If you decide to do this prank understand that it could be a career-limiting move if you do it to your boss and/or somebody without a sense of humor. I would also recommend to first experiment with a dummy keyboard that you don’t mind destroying.

I will not be held responsible for your problems. ;o)


To start you’ll need, of course, several musical greeting cards. Hallmark stores usually have a section dedicated to these cards. You’ll also need these tools and supplies:

Tools & Supplies
  1. Screw drivers (Phillips and a wide slotted)
  2. Needle nose pliers
  3. Soldering iron + solder
  4. Thin wire (22 gauge works well)
  5. NPN transistor
  6. Electrical tape

I went out and bought a CoolHeat soldering for this project due to its great portability. If you get one of these be sure to purchase at least 2 replacement tips as they’re pretty brittle and WILL break during normal use.

Getting Down to Business

1) Getting the music. The first thing you want to do is remove the musical element from the greeting card and cut off the excess paper.

Cutting out the musical elementMusical Element

2) Switch work. We now need to replace the metal switch with your transistor. First, let me define the parts of the switch I’ll be talking about. The bendable metal part of the switch I’m calling the metal tab, and thing it connects to, or touches, I’m calling the switch contact area.

Take the transistor and bend the center pin back slightly. Then slide the transistor onto the musical element switch area with the outer pins on top and the center pin on the bottom (see picture below & a better picture with notes here). Now make sure the left pin is resting on top of the switch tab and the right pin on the contact area.

Adding the transistor

Using your needle nose pliers bend the metal switch tab back over the transistor pin and make sure it holds it tightly. Now solder the other pin to the switch contact area.

Solder in Transistor

3) Lets wire it up. Cut two lengths of wire about 12 – 15 inches long. Solder one to the switch contact area (see black wire in picture above) and other to the center pin of the transistor (picture below).

Solder center pin

At this point you’ll want to use some electrical tape to tape down all the transistor pins and protect them from being pulled on.

4) Deconstructing the keyboard. Using your phillips screwdriver remove all the screws from the bottom of your keyboard. FYI: On some keyboards there are screws hiding under the rubber feed. Then use the slotted screwdriver to separate the keyboard halves. Be very careful with this step, as it’s likely to create visible damage.

Take apart the keyboard

5) LED setup. Find the LED and locate the positive and negative pins. Fish the wires from the musical element up through the keyboard and to the LED. Solder the wire from the center transistor pin to the positive LED pin and the other wire to the negative pin (the image below is from an ergo keyboard).

Attaching to the LED in an ergo keyboard

6) Finishing up. Now close up the keyboard, screw it back together and tape the musical element to the bottom. You’re done, plug it in and try it out!

Tape the musical element to the bottom of the keyboard Add a friendly note


Late one night I went into the office and carefully chose 3 keyboards to terrorize and an hour later I was done. The following day the first guy got the music playing right away, since he always uses caps instead of shift. He was baffled for a couple of hours, muting the sound on his computer and still wondering why it was making noise. Eventually he turned over the keyboard to find my note, and got a good laugh out of it. Strangely enough, he didn’t want me to remove it.

The second victim found it sometime after lunch. I wandered by, acting as innocent as I could, and suggesting “Try turning your sound off” then asking “Did you install anything today? Could it be a virus?” She started getting a bit concerned and I couldn’t hold a straight face any longer and ended up giving away my guilt.

The last guy never uses caps, so after waiting 2 weeks for it to happen I coerced him to press the key. He did and we had a good laugh about it.

I still have 5 more units setup and ready to go, I just have to find more victims…

All musical elements

Final Thoughts

This has been a really fun project, and one I plan on doing again. There is, however, one thing I would like to improve: be able to hook up the musical element to any key on the keyboard. Earlier on I tried some simple solid-state bounceless switch circuits and they worked well on the breadboard, but not on the keyboard itself. The complete pathway to and from keyboard button has about 120 ohms of resistance, which seemed a bit too much for the small battery. If anybody comes up with a solution, please post it in the comments section here.

Me with my creations

I want to hear about your experiences. If you decide to implement this project, please post your story in the comments section here.

Vote For Me
If you like this project, please vote for it on instructables.com.


  1. Connect a reed switch to the music circuit mount it under someones office chair with a magnet. When they turn to answer the phone or use the computer it starts playing. Use low, low volume so when they turn back to ask if you heard that it shuts off and you pretend you don’t hear a thing.

  2. Lazy Weekend Links…

    Here are this week’s Lazy Weekend Links…  Enjoy! Check out the Hammerhead, the CD thrower, which is a Mindstorms robot that throws CDs. Feel like pulling a prank on the ones you love?  Hack their keyboards and turn them into singing keyb…

  3. follow-up, embed a small magnet (radio shlock 2 rare earth for 1.79) under a keycap with the reed switch inside the keyboard, when the key is pressed the music circuit turns on. I don’t think you have to be concerned about debouncing to much.

  4. That’s hilarious. A buddy of mine on his last week of work pulled a prank where he reversed the wires on my boss’ mouse, so left-right was up-down. You should have seen him trying to login to the network in the morning, then throwing his mouse across the office.

  5. […] Here is a cool trick to play on someone. Make their keyboard sing when the caps lock button is pressed. Read more about it at The Mozmonkey Blog. “Take the musical element from a musical greeting card and connect it to the caps lock LED on the user’s keyboard. Each time the victim presses caps lock the music plays (and quite loud too). This is a great sleeping prank…It might be found on the first day, or weeks from implementation. It’s the perfect prank.” […]

  6. You could easily do this with any key by putting a PIC micro either in the keyboard or at the end of the cable between the keyboard cable and the puter and actually reading the data sent to the computer to determine which key has been pressed. Someone should make it have a different note for each of the middle row of letters!

  7. HOW TO – The Singing Keyboard prank…

    It doesn’t need to be April 1st to do pranks, here’s a really clever one, making a keyboard sing – “Take the musical element from a musical greeting card and connect it to the caps lock LED on the……

  8. I’m kinda slow and backwards but it seems to me you could use a mosfet with a latch to achieve the desired results.

  9. This is a good idea to keep from accidently pressing Caps-lock. I just remapped the capslock key in Windows to do nothing.

  10. My fav office prank is to take a screenshot of someones desktop and use that as the wallpaper. You minimize the toolbar and move the desktop icons off screen.

    They’ll be clicking for hours!

    Good times!!

  11. yo Says:
    >> all you guys are a bunch of geeks

    And proud of it. Awesome “mod”. πŸ™‚

  12. Some of the cards use sound effects instead of music.

    My parents have a card that farts, and a card that does a wolf whistle. The latter could definitely cause problems in a work environment…

  13. Ahhh man, this is THE perfect gift for all those people who always, ALWAYS (used shift for that :P) type with caps lock on, no matter what. Mad kudos to you for this ingeniously simple idea!

  14. What a great idea… even tha engadget.com are promoting ur idea. Keep up the good works…

  15. The Singing Keyboard prank…

    This hack isn’t really rocket science, and it’s not really a
    showstopper either, but it does provide the opportunity to cause a mild
    amount of annoyance to a coworker for relatively low cost and hassle —
    how do you beat that? It’s all explai…

  16. then, there is always the ide of switching the n and m keys around… or the two backslashes…

    but otherwise, gret prank.

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  18. I know very little about semiconductors and assume that the choice of NPN transistor is not critical.
    However, as I’ll have to buy some specially, I may as well buy something suitable for the application, so can anyone out there recommend a suitable component? I’m in the UK so would buy from Maplin.
    This is a great prank and I can’t wait to try it.

  19. I have an idea. why don’t you hook it up to a button and hide the button under the key? it might work with the SHIFT key… mehehe…

  20. I read this about a year ago and thought it was great, now im wondering if it can be greater… do you, or anyone else out there know how to change the sound on the card, if at all possible, or rig it to play a sound from another storage device?

  21. SWEET! Just finished ‘er up on a co-worker’s ‘board, as he’s out for the week on vacation…….gonna be good Monday when he gets back! Pranks period, are good…who cares if it’s April Fools day!?!