Turn your NFC / RFID implant into a theremin!
Well, you also need a Proxmark3, and you mustn’t be too picky about the “music” it generates 
But who knows? If you’re feeling creative…
More seriously, it’s actually quite useful to determine quickly the best spot and chip orientation to maximize coupling with the antenna, before doing a write for example. And because it doesn’t actually try to pull data out of the chip, the pitch starts to change several centimeters away from the surface, even with HF implants.
Here’s the Python script:
#!/usr/bin/python3
### Parameters
# Sound output parameters
volume = 1.0
sample_buf_size = 44
sampling_freq = 44100 #Hz
# Frequency generator parameters
min_freq = 200 #Hz
max_freq = 2000 #Hz
# Proxmark3 parameters
pm3_client="/usr/local/bin/proxmark3"
pm3_reader_dev_file="/dev/ttyACM0"
pm3_tune_cmd="hf tune"
### Modules
import numpy
import pyaudio
from select import select
from subprocess import Popen, DEVNULL, PIPE
### Main program
p = pyaudio.PyAudio()
# For paFloat32 sample values must be in range [-1.0, 1.0]
stream = p.open(format=pyaudio.paFloat32,
channels=1,
rate=sampling_freq,
output=True)
# Initial voltage to frequency values
min_v = 100.0
max_v = 0.0
v = 0
out_freq = min_freq
# Spawn the Proxmark3 client
pm3_proc = Popen([pm3_client, pm3_reader_dev_file, "-c", pm3_tune_cmd],
bufsize=0, env={}, stdin=DEVNULL, stdout=PIPE, stderr=DEVNULL)
mv_recbuf = ""
# Read voltages from the Proxmark3, generate the sine wave, output to soundcard
sample_buf = [0.0 for x in range(0, sample_buf_size)]
i = 0
sinev = 0
while True:
# Read Proxmark3 client's stdout and extract voltage values
if(select([pm3_proc.stdout], [], [], 0)[0]):
b = pm3_proc.stdout.read(256).decode("ascii")
for c in b:
if c in "0123456789 mV":
mv_recbuf += c
else:
mv_recbuf = ""
if mv_recbuf[-3:] == " mV":
v = int(mv_recbuf[:-3]) / 1000
if v < min_v:
min_v = v - 0.001
if v > max_v:
max_v = v
# Recalculate the audio frequency to generate
out_freq = (max_freq - min_freq) * (max_v - v) / (max_v - min_v) \
+ min_freq
# Generate the samples and write them to the soundcard
sinevs = out_freq / sampling_freq * numpy.pi * 2
sample_buf[i] = sinev
sinev += sinevs
sinev = sinev if sinev < numpy.pi * 2 else sinev - numpy.pi * 2
i = (i + 1) % sample_buf_size
if not i:
stream.write((numpy.sin(sample_buf) * volume).
astype(numpy.float32).tobytes())
