The answer isn't off-keyness, although I wish it were.
I am interested in the secondary meaning of something being off-key, in the sense that it is irregular or incongruous, for example: "An off-key remark" and "His remark was off-key"
Oxford Dictionaries provides this example:
You try to console her, but it feels a bit off-key: after all you’ve heard only 70% of what she’s said.
In Italian, the adjective off-key is translated by stonato, which means something is out of tune (tone = tono) and intonato.
He sang on-key/in tune = Lui era intonato
He sang off-key/out of tune = Lui era stonato
I need a noun that fits the sentence below:
A) The phrase "I transported my friend to the airport" sounds off-key, if we swap the verb, transport with "took" the _____ no longer occurs.
The Italian noun form is stonatura, below is an example of how it is used and my translation:
Quel gilet viola è una stonatura intollerabile
B) That purple waistcoat (AmEng vest) is an unbearable ____
- What noun can fill both gaps, i.e. A and B?
EDIT
Dissonance fits perfectly in example A, but much less so in B. The problem is a visual _____, because the speaker is complaining about the colour. Perhaps the purple is jarring per se or it clashes with the shirt. What noun describes this visual disharmony?
Is there a better noun than dissonance and discordance as suggested by @Mitch and @Third News to complete sentence B?