Indeed if we have to be true, the plot of Out of Tune is not so much different from the other book I read by Fabian Black, Moving On, but in a way this is better since the story seems to have a more rational meaning and in a way it seems more realistic and possible. Plus, in any case, I read both Moving On and Out of Tune with the same interest, not caring at all that the stories were similar.
As for Moving On I have to highlight that the D/s side of the story is completely different from your usual BDSM romance: here the punishments Gordon sometime bestows on Nat are not at all preamble to their lovemaking, they are a real good spanking since Nat had behaved like a bad boy; and after the punishment he is sent to bed without dinner, exactly like any other romp boy. There is absolutely no sex, actually there is really few sex in all the story and it's not related to the punishment.
Gordon is a psychiatrist working for the National Health System in a beginning of the '80 London; I think the author chose the 1981 and 1982 to set his story since it was probably still a period in time when depression and other behavioural comportment were still classified as mental issue and treated as such. Plus that was a time when being gay was still a danger to your social status. Gordon meets Nat in a professional moment, in a hospital ward as his patient; of course as soon as Gordon realizes he has deep feelings for Nat, he voluntarily stops to be his doctor letting him being taking care in that facility by a good friend, but he decides to become Nat's lover and protector. From what I said before about their relationship, more than a D/s relationship, someone could think theirs is more a Daddy/boy one; but actually is neither like that: I have never felt like Gordon is attracted by Nat since he sees him like a little boy who needs to be take care of, or that Nat is searching in Gordon a lost father; their relationship is really more that of a doctor with a patient, only that once the doctor falls in love with the patient, and the feeling is mutual, they cannot rightly continue on that path, but that doesn't mean that Gordon doesn't know what is the best for Nat, or that Nat doesn't know that Gordon is doing everything he does out of love for him.
The novel is the collection of two novellas each of them set during a different Christmas, 1981 and 1982. I liked that since it gives the reader the chance to see that indeed, the relationship born in 1981 lasted and grew in the following year but it's not that everything turned out right out of the blue; Nat has real and big issues he will need time to overcome, Gordon is not a magician with a wand, he is a good, but ordinary doctor, and they will have to work together to reach the same target.
What probably I liked the best in all the novel are the intimate moment between Gordon and Nat, something that was completely estranged by sex and strangely for that reason was even more deep.