Where are we to infer that the bug was planted in The Conversation?

(For reference, here is the scene)

There might not be a bug

Screenwriter and director Francis Ford Coppola candidly admits that he never decided whether there was a bug to begin with.

In his screenplay (available for download; pdf) (starting on page 155), Harry's search is described in detail, but makes no hint as to where the bug might actually be. It merely reads:

He has not found the tap, if one exists.

In the DVD commentary (available for streaming or download; mp3) (starting at 1:49:06), Coppola says:

"The other most asked question to me ... is where was the bug that bugged Harry at the end? Of course many people have their theories. One notion was that it was in the plastic Madonna that he had in his apartment but he thinks of that himself ... indeed it does not turn out to be there.

"... The other possibility ... and the theory that I always imagined might be the case, was that it was in the little saxophone strap, that little clasp in the saxophone that was hanging around his neck during all the time that he was there ... but that was never confirmed or disproved.

"... And then again of course there is always the possibility that there was no microphone, there was no bug, that the microphone really was more in Harry's degenerated state, in his personal madness brought on by this story and what had happened.

"I know it's very difficult for you to accept from me, but the truth of the matter is I don't know where the microphone bug is."

Difficult to accept indeed!

How finding a bug would change the scene

40 years later The Conversation remains a spectacularly relevant character study and is prescient in its depiction of the slow burning psychological strain of life under surveillance. Its final scene is iconic, and its strength is its ambiguity.

To me, the point isn't whether Harry finds what he thinks he wants to find, but his psychological desperation in searching. That there might be a bug is the straw that breaks the camel's back. We witness a composed man finally give in to deep rooted frustration and paranoia. By the time he resorts to tearing up the floors it's a moot point whether the bug is still in the apartment. Finding it will not assuage his guilt or lessen his complicity in the acts that led up to this; his violated sanctuary is no less violated; discovery is not resolution, only confirmation, the redundant inconsequential kind obsessively pursued by the powerless. Harry is profoundly psychologically burdened, and it culminates in him destroying his home.

In this sense, I think not finding the bug is far from a plot inconsistency. Finding it would weaken the scene. Harry literally and symbolically "comes up empty" which amplifies everything else and ends on a poignant character note. If the bug exists, so be it, but if he finds it, the ambiguity is removed, Harry is vindicated at least in that moment, and the significance of his desperation is diminished.

I must have seen The Conversation 8 or 10 times over the years, and it's my favorite Coppola. I watched it again this evening. What a subtle mind trip! Sure, the eavesdropping equipment we see is out of date now, but the underlying ideas aren't. I wholeheartedly agree with rbsite, Harry finding the bug would have been a letdown for the audience. Why? Because it would be like stuffing the genie back in the bottle: the endless possibilities for spying with technology not only can make individuals paranoid and lose their minds, that state of affairs warps our whole social reality. A covenant of trust among members of society is shattered. You can make a psychological explanation for Harry's "visions," yet you don't have to--he might be seeing and hearing things as they are, but "things as they are" have been reduced to a slippery tumult of "facts" that can't be used to establish anything. That's the sad outcome of a world in which people can't rely on others to be above board, tell the truth in the most basic ways and respect others' dignity and privacy. Sorry if I've been a little sketchy, but I think that loss, or the impending threat of it, is the larger point of Coppola's film. The movie isn't only a psychological portrayal (great as that layer is) but about the destruction of a common understanding of the world when we can't trust each other.

It's a great film, I agree with you all. In my view though, FFC is being mischievous with his comments.

There is a scene (from memory) during the convention, and across the back of that scene a man walks by holding a tenor sax. Bearing in mind this is a film set, of which FFC would have control, that man is not on screen holding a tenor sax without a direction from FFC to do so. That suggests to me that FFC dropped a clue as to the whereabouts of the bug.

It'd be good to hear views on other reasons for FFC might have directed this scene.

As to the emphasis on Harry's psychological state, I'd suggest that the obsession with finding the bug is not as interesting as the larger obsession with professional perfection. He's come across someone who can bug better than he can. If he figures out the puzzle, he can regain his position of professional perfection. Until then, he has met his match, and he's not the professional he thought he was.

Related, his professional perfection, for him, means doing everything himself. He doesn't buy: he builds his own. He doesn't even practice with a band. He practices alone with a tape as proxy for accompaniment. That he practices alone mirrors his need to be perfect alone, as opposed to having the perfect team--employees who he can learn from as much as teach. Such aversion to others may derive from paranoia, as does his desire to snoop on others. This, I think, is the more profound comment on his psychological state to be inferred from the scene, not that he is paranoid about what may not even be a bug.

I wouldn't worry too much about FFC's not having a proper solution. "The Big Sleep" had holes too (who killed the chauffeur?), because the writers were more interested in character than the puzzle-solution payoff. Some would call it deliberate ambiguity. I call it indifferent writing.

But maybe not. He made a mistake about the girl's murder. He gets in trouble when his information is inadequate. He thinks he gets the inside information with his bugs, thus granting him omniscience. He learns that this is not true. Then he tears up his apartment because he doesn't have enough information about the location of what recorded his sax practice. Lack of information is an itch that, lately, he finds he can't scratch. Perhaps FFC was giving the audience a taste of what it felt like to have such an itch by deliberately having no solution to the bug hunt. This seems to be a new take on an old Hitchcockian theme: identifying the audience as voyeurs, as in "Rear Window," showing tortured voyeurs who got their facts wrong due to a few gaps.

Then there's the Hitchockian theme of the perpetrator of a seemingly victimless crime getting a taste of their own medicine. In "Rear Window," the voyeur becomes the viewed, and gets a taste of his own medicine. Similarly, lying adman Roger Thornhill (sorry, "expedient exaggeration") of "NxNW" finds that people no longer believe him, including the police. He gets manipulated by those who practice deceit on a much larger stage.

At the end of the film, Harry is now bugged, and it bugs him.

http://www.gradesaver.com/the-conversation/study-guide/summary-part-5-the-murder

May be the bug was in the harry's eye glasses because once he left his glasses at his girlfriend house for a little bit of time. There was also a scene which indicated it in the ending where the girl who were spying by harry was kissing her boyfriend with touching his eye wear.

I agree with the saxophone theory and the scene with the saxophone being carried across frame. This coupled with the scene where Caul tells his landlord that he has no personal belongings in his apartment. This likely rhetoric to keep his landlord from reentering, but in every interpersonal interaction he does his best to be a man with no past or personality. But one of the first characterizing moments is of him playing along to a recording and at the height of his madness he destroys his communications equipment, his religious symbols, and his house but leaves his saxophone untouched. This can signify it as his most prized and intimate personal belonging and in turn a chink in his armor.

It is also a fitting end that the greatest wire-tapper in the country ends the film amidst the literal and figurative rubble of his life playing the instrument that may have played a major role in his downfall as it was the one personal item he couldn't give up or suspect.

Inside the light bulbs of Harry Caul's apartment.

The bug was in his glasses. The hooker who stole the tapes put the bug on his glasses after he fell asleep. His so-called "friend"/"rival" brought the hooker for that reason. The 'friend/rival" was working for the director's assistant.

Of course there's a bug - how else would they play back his sax playing? I'm certain it's in the hinge on his spectacles.

The saxophone is too obvious. As to the theory that it was safe to put it there because he'd have to break his sax to find it and he'd never do that - well, if they can put it in there without breaking it, then he can find it without breaking it. And anyway, he can always buy another sax. Given his paranoia and need for privacy, a destroyed saxophone is a small price to pay.

The clue is almost the penultimate cut in the film, as he plays sax in the wreckage of his destroyed flat, which is a flashback to the couple in Union Square - and of all the shots FCC could have chosen, it's the one where the girl turns to the man, slightly lifts his glasses and takes something out of his eye. Why? Why put any flashback shot there, and why that one, if he isn't taking our attention there?

Meredith, the hooker employed to steal the tape, was also tasked to place the bug; we see her take his glasses off and lay them beside the bed before she gets in with him. She was probably employed at the trade show by Harrison Ford, one of the three conspirators. We know he visited the show - we thought it was to see Harry Caul. But in retrospect, it was also to recruit someone to steal the tapes. Whether he arranged it all through Bernie Moran, (Alan Garfield, an astonishingly good performance, you almost have to wash your hands after every scene he's in) for whom she is working, is moot.

But as one other poster here has said - it's the glasses.