Last summer, long before candidate Jenny Durkan admitted that the last live music show she'd seen was The Eagles, a well-funded political action committee had come to the conclusion that it would be good for Durkan to reach out to this city's music lovers.

So the group, "People for Jenny Durkan," dropped $15,000 on an ad promoting Durkan on the music streaming service Pandora. Here's the ad, which came with a guitar lick that Stranger music writer Dave Segal describes as "a distant, sterilized echo of grunge."

Pandora is headquartered in Oakland with an office here in Seattle, and it tells potential advertisers that it's able to observe "over 1 billion data points every day" on its platform. The company uses all that data to "ensure our partners are engaging with the most relevant, high-value audiences."

It's all a reminder that targeted digital advertising is a major money-maker for companies beyond Facebook and Google.

Pandora brags that "whether you want to reach fitness-driven moms in Atlanta or mobile Gen Z in Sioux Falls, Pandora’s targeting platform allows us to zero in on your audience." And it's not just the Durkan PAC that's been taking the company up on its offers. Two other local candidates, Scott Lindsay and Sara Nelson, targeted users of Pandora with election ads in 2017. So did the Trump campaign in 2016, according to The Cambridge Analytica Files.

So it's worth knowing: Which local audience, exactly, was "People for Jenny Durkan" trying to zero in on with this Pandora ad during last year's mayoral primary?

What winning Pandora playlists was this ad pressed up against? What "mobile Gen Z" types or reliably-voting Eagles fans were targeted to hear it?

The story of how I've tried, and so fair failed, to get this relatively minor bit of information begins months ago, on December 19, 2017, when I showed up at Pandora's Seattle office with a copy of a unique Seattle law.

That law says companies like Pandora have to disclose, upon request, "the exact nature and extent" of the political advertising services they've offered when it comes to Seattle elections. So I buzzed Pandora's Pioneer Square offices and...

...after explaining myself, was not let inside.

A very nice receptionist came down and promised to pass along a letter I'd brought with me, as well as a copy of the Seattle law. To make sure my request reached the right eyes, the next day I e-mailed Pandora's spokespeople.

Months of very slow negotiation ensued, during which Pandora consistently declined to give me more than this (.PDF), which arrived in my in-box in late December. It's a very basic summary of who spent what on Pandora ads targeting Seattle's 2017 municipal elections.

Granted, that's more than Facebook or Google released in December or January in response to identical requests I'd made at their local offices—requests that were made well before I showed up at Pandora's Seattle office.

Still, it was hard to see how Pandora's initial disclosure revealed "the exact nature and extent" of all ads it sold targeting Seattle's 2017 elections.

The group "People for Jenny Durkan" wasn't any help, either. It hasn't responded to any of my e-mail and phone requests over the last two months. (But Sandeep Kaushik, a consultant for Mayor Durkan, did clarify, shortly after this story went up, that the Eagles concert occurred "literally three days" before Durkan admitted The Eagles had been her last live show—a fact not mentioned in previous Stranger reporting.)

In late February and early March, after Google and then Facebook sent the City of Seattle their first substantial disclosures of local political ads, Pandora changed its mind. On the Monday after the Cambridge Analytica scandal broke, I received an e-mail from Pandora spokesperson Jette Speights.

"Although we believe that our original production fully complied with any obligations Pandora has," Speights wrote, "in light of recent additional informal guidance from the Seattle Ethics and Elections Commission, we will agree to supplement our initial disclosure."

What was this "additional informal guidance" Pandora had received?

I asked Seattle Ethics and Elections director Wayne Barnett whether his office had issued any such guidance to Pandora. He said it had not. I asked Speights what "additional informal guidance" was being referred to in the company's e-mail. I received no reply.

But Speights had now supplemented Pandora's original, limited disclosure with audio files containing the three political ads Pandora ran targeting Seattle's 2017 elections—one for Durkan, two for failed City Attorney candidate Scott Lindsay, and one for failed Seattle City Council Candidate Sara Nelson.

The supplemental disclosure also contained some very basic information on each ad's targeting and cost, and the number of impressions it received.

Here are the Lindsay and Nelson ads that were recently released by Pandora:

And here's Pandora's supplemental disclosure (.PDF) of March 19.

The pro-Durkan ad, according to Pandora, was targeted at people over the age of 18 in the Seattle-Tacoma metropolitan area in the run-up to the August 1, 2017 mayoral primary. It received 558,465 impressions. (Suggesting that the number of people exposed to this one pro-Durkan ad on Pandora could have been greater than the total number of people registered to vote in Seattle and more than twice as large as the total number of people who actually voted in last year's primary.)

The pro-Nelson ad cost $12,500 and was also targeted broadly at people over the age of 18 in the Seattle-Tacoma metropolitan area.

The ads for the Lindsay campaign, according to Pandora, cost $13,400 and were targeted at 26 pre-selected Seattle zip codes. (Which is perhaps another sign of the Lindsay campaign's strong embrace of micro-targeting.) Every single zip code in North Seattle, for example, was targeted by Lindsay—except the one covering the University of Washington, which would have been on summer break at the time.

This is all interesting to know, but unless Pandora is way over-stating its targeting capabilities, then it's highly unlikely that the only options these three campaigns had for targeting Seattle voters via Pandora was to say, "Give me people over 18 in Seattle." (And, in the case of the Lindsay campaign, to add: "...but not in these zip codes.")

As Pandora itself says, the company offers "over 1,300 audience segments to date," a result of "a 100% registered user base" that's combined with the company's "rich 1st, 2nd and 3rd-party data to deliver highly engaged target audiences."

How, exactly, did "People for Jenny Durkan" use Pandora's robust targeting capabilities to help Durkan win the primary?

Although Seattle law says Pandora should publicly disclose the "exact nature and extent" of its services to this campaign, we still don't know.