Generating Music With Credit Cards


[Steve] was browsing around at a local electronics surplus store when he spotted an old Tranz 330 point-of-sale terminal that seemed pretty interesting. He took it home and after disassembling it, found that it contained a Z-80 based computer. Because the 330 shares the same processor as other hobbyist-friendly devices such as the TRS-80, he figured it would be quite fun to hack.

While the Z-80 processor is pretty common, [Steve] still had to figure out how it was interfaced in this particular device. After spending some time reverse engineering the terminal, he had free reign to run any program he desired. After thinking for a bit, he decided it would be cool to use the terminal to generate music based on whatever card was swiped through the reader – he calls his creation “Mozart’s Credit Card”.

He found that just playing sounds based on the raw contents of the mag strips didn’t produce anything coherent, so he wrote a small application for the terminal based on the Melisma Stochastic Melody Generator. Music is generated somewhat randomly using various card characteristics, as you can see in the video below.

We think it’s pretty cool, but [Steve] says he’s always open to suggestions, so let us know what you think in the comments.


19 thoughts on “Generating Music With Credit Cards

  1. I liked this project! Also, this is a great example of what a correctly done “project demo video” should look like. No shakey cam, good quality video, clearly spoken “to the point” words explaining what’s going on.

  2. It’s actually pretty easy (if time-consuming) to reverse engineer the Tranz 330s. They have the ability to list code and accept new programming through the keypad and LCD in addition to code loading over serial or built-in modem. TCL (not Tcl) programming documentation is probably available from the company on their website. If you see one of thse for cheap, pick it up to play with, especially if it comes with the thermal printer. Beware that the last programmer may have changed the “admin passcode” that lets you through to the code, though. Small chance, I’d guess.

  3. That is, it’s not too difficult to reverse the Tranz 330’s high-level function by dumping and examining/rewriting its native code. Getting it to the point where you can reprogram it with Z80 assembler, they way Steve’s doing it, is much trickier.

  4. I threw one of these away recently thinking I’d never have a use for it. Ok really, it was the girlfriend who said I’d never have a use for it.

    She’s long gone.

  5. I’ve seen several of these at our local Savers store this last month. WIth and wo power or printers. I grabbed one term with no acc. for 5 bucks thought it may come in handy latter.

  6. Credit card swipers for “evil hackers” have been brain dead easy for decades. a credit card reader is nothing more than an audio tape head. the small circuit to set it all up to record the credit card is brain dead easy. Hell I have seen some that worked with recording walkmans from the 80’s.

    Why the people that know nothing at all come out of the woodwork screaming about “stealing credit cards! WOOOOO!” every time a magstripe reader is used for something cool…..

    Suck it ankle biters wannabees… having access to a reader/validator terminal does NOT increase any risk of anything.

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