Doug, actually I have read and studied Robert Langs's works in detail, many of them. It was several years ago, however, so his terminology is not fresh in my mind. But I think I could probably give even now a rough summary of his basic theoretical approach. Many of his central concepts, if not his terminology, have stayed with me as a basic part of how I think about interpersonal communication, especially his use of three levels of communication that differ in depth of symbolic and affective associative meaning (A, B, and C, isn't it?).
His richly detailed clinical studies of unconscious communications of the patient's perceptions of the therapist's interventions make fascinating and persuasive reading. My favorite Langs book is one of his least technical ones titled The Psychotherapeutic Conspiracy. The title is a real teaser but the contents are tremendous.
Patrick Casement's short book titled On Learning From the Patient makes excellent and easy-to-read use of Langian ideas while Casement presents his own clinical cases, too.
Langs's approach can be complementary with Weiss's in many important ways. But Weiss adds important new dimensions to his theory such as, for example, survivor guilt, self-sacrificing altruism, and adapting the treatment approach to the patient's plans.
Weiss's and Langs's approaches are drastically different--about as different as two approaches can be--in one respect, however. Langs is a stickler for keeping rigidly to the classical pscyhoanalytic "frame" while CMT is surely not.
In fact, if I recall correctly, Langs argues that most important things the patient notices about the therapist will happen when the therapist violates the frame. Langs's studies of process notes are thoroughly convincing to me that patients have a fantastically good unconscous level of understanding of themselves and their therapists. I was left, after reading Langs, with the impression that one could even define emotional disturbance as a condition in which a person has an accurate and keen unconscious knowledge and perception of one's social world that is too powerful for the patient's conscious mind to yet tolerate. This is the important message, as I understand it, in The Psychotherapeutic Conspiracy, too.
CMT is not focused on keeping fast to a rigid frame. On the contrary, CMT has no necessarily fixed frame applicable to all patients. The therapist's behavior will depend upon what the patient needs from the therapist. But CMT also has it's own ways of understanding the patient's unconscious communications about what the patient wants from the therapist. CMT looks closely at changes in the patient's level of behavioral, cognitive, and affective confidence and organization following interventions. Langs does something very similar, too, in keeping his close watch on the patient's involvement at the deep level of associative communication as a marker of progress.
You may or may not already know that Theodore Dorpat, very much like Langs, also makes heavy use of unconscious meanings in the patient's communications that can inform the therapist of the patient's perceptions of the therapist's interventions. Dorpat, unlike Langs, also uses findings from experimental research in cognitive research (my general area--I'm not a clinician) as well as material from his own patients as well as from reports of others' patients.
Joesph Weiss is one the persons who recommended Dorpat's work on the dust jacket of Dorpat's recent book titled Gaslighting, The Double Whammy, Interrogation, and Other Methods of Covert Control in Psychotherapy and Analysis. I think, Doug, you would probably appreciate Dorpat's book as much as or more than I did. It is a useful critique of many conventional high-handed techniques and training methods used by some therapists and their mentors. Joe Weiss says on the cover of Dorpat's book "..[it] provides a much needed critique of current clinical practice."
Weiss further says of Dorpat's book, "...[it] shows us how the therapist using widely accepted techniques...may...induce the patient to accept the therapist's sometimes erroneous ideas." Dorpat's methods of deciphering a patient's communications about the therapist's interventions are parallel to those of Langs's, but Dorpat adds some information from cognitive research as well. As you can see, Jeseph Weiss clearly recommends that therapists understand these kinds of processes that you so rightly appreciate are also detailed well by the very creative Robert Langs.