score · Xyh Tamura, 2026
GRID = 150 Hz POSITIONS = 150, 300, 450, … 3750 Hz OMITTED = 900, 1200, 1800, 2400 Hz PROBE = POSITIONS without OMITTED ANNOUNCE = 2100 Hz, amplitude-modulated at 15 Hz, reversing phase every 450 ms CAPABILITY = frequency-shift keying at 300 bit/s RATES = an ordered list, fastest first, with a minimum bandwidth and signal-to-noise ratio for each rate.
choose the total duration and every value in brackets.
sound a telephone line for the whole duration,
at the edge of audibility.
its noise consists of band-limited hiss, mains hum,
and [ occasional ] impulses.
as the piece progresses, with fluctuations:
attenuate the line until it carries nothing
attenuate high frequencies more than low frequencies
raise the noise, then hold its level
move a narrow null down through the band
from each attempt, sound only [ a few ] fragments. for each fragment: length drawn so short ones dominate, none longer than [ about a second ] source any available one of: announce, probe, capability, or data time anywhere within a window [ wider than the interval between attempts ] position between the two ends of the call level at or below the level of its source as the piece nears its end: sound fewer, shorter fragments.
repeat every [ a few seconds to half a minute ] for the whole duration:
1 announce emit ANNOUNCE for [ one to four seconds ].
2 probe emit PROBE at equal amplitude. set its phases to minimise the combined peak. first [ briefly, raised ], then [ longer, nominal ].
3 measure let RECEIVED = the probe, through the line, plus its noise. for each f in OMITTED and each midpoint between positions: noise[f] = power of RECEIVED at f for each t in PROBE: snr[t] = power of RECEIVED at t, against noise interpolated to t
4 decide USABLE = { t in PROBE : snr[t] ≥ [ a threshold ] } if |USABLE| < 2: RATE = NONE else: BANDWIDTH = |USABLE| × GRID QUALITY = mean of snr over USABLE RATE = the first r in RATES with BANDWIDTH ≥ r.least_bandwidth and QUALITY ≥ r.least_snr, or NONE
5 speak emit CAPABILITY from both ends, overlapping, carrying the measurement. if RATE is not NONE: emit data at RATE, shaped to the chosen band, for a time [ increasing with RATE ].