Talk about stubborn. Larry Cotton, a retired engineer Each hand-soldered circuit drove relays and
from New Bern, N.C., didn’t want PC hardware higher-current solenoids (former cassette player
anywhere near his elegant marimba, even though mechanisms bought surplus).
it would have made things a lot easier. Most makers Cotton makes custom rolls himself by playing
connect instruments to a computer via MIDI or songs on his piano and capturing the audio on
some other common interface. Cotton had to rig his workshop PC. By running it through Cakewalk
up a low-tech optical reader inside the marimba 6.0 software, Cotton is able to reformat the MIDI
to play custom piano rolls. “I was just kind of doing computer dots to play in his machine.
my own thing, committed to using nothing that The oddly shaped marimba pounds out a mean
existed already,” says Cotton. version of Flight of the Bumble Bee, along with the
He started with photodiodes and 300-pound old Carmen Miranda tune “Tico Tico” and other
fishing line. He shined spotlights through the thick songs. But like nearly all player instruments, you
monofilament, creating a cheap fiber optic system. can tell the difference. Asked if there are times
He lined up 40 spots across 4 inches of makeshift you can almost close your eyes and hear a human
roll, each one accounting for one of the 37 hand- player, Cotton laughs. “Oh, yeah,” he says. “A pretty
made oak bars around the circular instrument. bad one.”
An inkjet printer furnished black dots on the trans- —Bob Parks
parency, and when the dots blocked light, a voltage
change from the photodiodes registered to Schmitt
triggers and 555 timers.