So I have come across a difficulty in my harmonic analysis having to do with the tritone being by itself. Obviously, this gets across a dissonance that has to resolve but just from the tritone, it isn't clear which dissonance it is supposed to represent because there is no third or seventh, just the tritone.

The tritone I came across is the same one I usually come across in my canons as a diminished triad. But in this case, all I really know is that it is used as a dominant, not which one. On the one hand, assuming it is A diminished makes the fewest assumptions because the only note not present is the third. Eb diminished, while it does have the same tritone, is not diatonic to Bb major. It is a chromatic alteration of Eb major in the case of the key being Bb major.

F7 is the only other diatonic chord which has the same tritone but for one thing, I hear no F or C, the first and fifth notes of the F major chord which F7 is based off of. Also, according to the harmonic analysis of the canon I am currently analyzing it resolves to Eb major. This along with the bass note of Eb suggests that it is Eb diminished without the Gb. 

But that is a chromatic alteration of Eb major in the perspective of Bb being the tonic. And diminished chords rarely if ever resolve to the major chord of the root. They usually act as a dominant chord. So is this A diminished then or is it just an A/Eb dyad?

EDIT: Here is the section of the score with the harmonic ambiguity of the tritone:

[![enter image description here](https://i.stack.imgur.com/3HgNt.png)](https://i.stack.imgur.com/3HgNt.png)