  We explore a basic noise-free signaling scenario where coordination and
communication are naturally merged. A random signal X_1,...,X_n is processed to
produce a control signal or action sequence A_1,...,A_n, which is observed and
further processed (without access to X_1,...,X_n) to produce a third sequence
B_1,...,B_n. The object of interest is the set of empirical joint distributions
p(x,a,b) that can be achieved in this setting. We show that H(A) >= I(X;A,B) is
the necessary and sufficient condition for achieving p(x,a,b) when no causality
constraints are enforced on the encoders. We also give results for various
causality constraints.
  This setting sheds light on the embedding of digital information in analog
signals, a concept that is exploited in digital watermarking, steganography,
cooperative communication, and strategic play in team games such as bridge.
