20 Questions

My housemates Jodi and Mark are members of Invisible. Mark is co-creator of the Selectric Piano (and the dancer in this video); Jodi is at the keyboards. This description is from Invisible’s MySpace page:

“Here’s a Video of the song 20 Questions, performed earlier this year at 1001 in Greensboro. It features Jodi on the Selectric Piano, an instrument built by Fred Snider and Mark Dixon that interfaces a typewriter with a piano. notes and letters. The video was shot by Jon McLean and edited down by Bart Trotman.”

Tech info on the Selectric Piano:

“To begin with, the IBM Selectric typewriter is a marvel of engineering! The typewriter is 100 percent mechanical and employs a 6 digit binary coding system to direct its type ball to the proper latitude and longitude for each character that the typist types. To access that six digit code we placed tiny light sensing switches at each of six bars that transfer the keystroke to the type ball. The shift command adds another switch and thus a seventh digit to the code. That code is “cleaned up” electronically by circuits we mounted on the typewriter itself. The code is then sent via a printer cable to the piano playing assembly. There we use chips called ‘demultiplexers’ to translate the seven-digit binary code into a base-ten number between 1 and 88. Amazingly, the IBM Selectric types exactly 88 characters — that’s the number of notes a piano plays! That demultiplexed signal is amplified to 33 volts on its way to to contract the appropriate solenoid. Each key has its own dedicated solenoid and ‘finger’ assembly made from our plastic cutting board, some hard maple and brass rods for pivots. The piano-playing assembly sits in front of the piano on a bench. It is not permanently attached to the piano. Jodi applies sustain via a douglas fir two by four which is attached to the piano’s sustain peddle using two bent nails.

“Incidentally, some of the first ‘letter quality’ computer printers were IBM Selectrics that were rigged to computers in the exact opposite way as described above. Solenoids operated the typewriter’s six bars, shift and return functions. This was available as a package conversion but many old school hackers like Fred, one of the makers of the Selectric Piano, made their own at home.”

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6 Comments

Filed under movie of the week

6 responses to “20 Questions

  1. Noel Kirby-Smith

    I sort of enjoyed 20 Questions, but I was unhappy to see the camera focussed almost only on the men doing what they’re doing and then regular, brief shots of Jodi’s fingers typing. I felt like I was watching an old movie on tv, one in which a boss says, “Miss Whoever, take a letter.” Yes, I know we saw a glimpse of the side of her face every now and then, but, really! What Jodi was doing was the most interesting part of the performance. But she was the only real “Invisible.”

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  3. That typewriter is absolutely brilliant!

    Are there technical details available? I have a jammed Selectric or two myself that I should see about repairing.

    Please reply to my email:

    toresbe “curly letter a” ifi “period” uio “dot” no

  4. j.

    Check out the full descrpition of the Selectric Piano, along with other musical creations at the INVISIBLE page:
    myspace.com/invisiblesounds

  5. mark dixon

    Hey thanks. here’s a little brief on what’s going on within the Selectric Piano. Not super technical though!

    To begin with, the IBM Selectric typewriter is a marvel of engineering! The typewriter is 100 percent mechanical and employs a 6 digit binary coding system to direct its type ball to the proper latitude and longitude for each character that the typist types. To access that six digit code we placed tiny light sensing switches at each of six bars that transfer the keystroke to the type ball. The shift command ads another switch and thus a seventh digit to the code. That code is “cleaned up” electronically by circuits we mounted on the typewriter itself. The code is then sent via a printer cable to the piano playing assembly. There we use chips called “demultiplexers” to translate the seven digit binary code into a base-ten number between 1 and 88. Amazingly, the IBM Selectric types exactly 88 characters — that’s the number of notes a piano plays! That demultiplexed signal is amplified to 33 volts in order to contract the appropriate solenoid. Each piano key has its own dedicated solenoid and “finger” assembly made from our plastic cutting board, some hard maple and brass rods for pivots. The piano playing assembly sits in front of the piano on a bench. It is not permanently attached to the piano. They typianist applies sustain via a douglas fir two by four which is attached to the piano’s sustain peddle using two bent nails.

    Incidentally, some of the first “letter quality” computer printers were IBM Selectrics that were rigged to computers in the exact opposite way as described above. Solenoids operated the typewriters six bars, shift and return functions. This was available as a package conversion but many old school hackers like Fred, one of the makers of the Selectric Piano, made their own at home.

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