Once word started circulating about the songwriting app that Aaron Shekey and Joseph Kuefler are launching, fellow musicians have been wanting to show off their own personal messes.

"The reaction is always, 'Oh my God, you have to see all the memos I have on my phone!' " Shekey recounted.

When inspiration strikes, songwriters want to capture it ASAP. Keith Richards, as legend has it, would have forgotten the immortal riff of "Satisfaction" without the little cassette recorder he had one night while drunkenly strumming his guitar in a hotel room.

Today's budding rock stars have a different device readily at hand: their cellphone. Only problem is, mobile phones are also where we control many other facets of our lives, "so your song ideas wind up between your grocery list and your notes for work, or whatever," Shekey said. "You wind up losing a lot of your ideas, or spending all your time looking for them."

Thus came Hum, which hits the iPhone App Store this week, offering a portable demo-recording studio for those lightning-strikes ideas.

Available for a limited time for $1.99 (it will soon go up to $4.99), Hum is equal parts audio recorder and note taker, with the capability of typing out lyrics, sorting through musical keys, organizing song ideas by title, editing different tracks and sharing the results with bandmates. Most of that can be done on iPhones already, but not on the same app.

That the idea came from two Twin Cities musicians — self-described as "musicians at heart who also happen to be tech nerds" — and not a Silicon Valley software company is one of the main selling points.

"We wanted this for ourselves first and foremost, and we had ours and our friends' interests in mind to make the [songwriting] process that much easier," said Shekey, 27, who fronts the indie-rock band Usual Things.

A Madison, Wis., native, he moved to San Francisco from Minneapolis a few years ago for a high-tech job with Adobe Systems but returned to go into freelancing. "I couldn't stomach paying three times as much on rent as what a mortgage payment is in Minneapolis," Shekey said.

Kuefler, 30, made a local splash a few years back playing keyboards with the Alarmists. Now he has a music-related computer job for Audiofile in Minneapolis.

"There's no reason Minneapolis can't be seen as the kind of creative-minded tech center that Silicon Valley is," he said. "Especially for what we're starting, there's so much creative energy and smart people here to pull from."

In the works since May, Hum has been test-driven by a variety of Twin Cities musicians, including such well-known names as John Hermanson, Mark Mallman and Ed Ackerson, plus some rappers and even a metal guitarist. ("It's not just for singer/songwriters," Shekey noted.)

"I've been using it even more than I thought I would," said Hermanson. Best known from the folk duo Storyhill and pop-rock bands the Hopefuls and Alva Star, he also has created music for national TV ads.

Hermanson used the app during a recent getaway Up North. "I normally operate in front of a computer, but in this case all I had was my phone, and it worked great," he said. "It really involves a lot of otherwise simple functions, but it's nice having all those functions together and not have to bounce around your phone."

Shekey and Kuefler are hoping Hum users like him will spread the word. In fact, they're banking on it. While they have invested almost $10,000 in making their idea a reality, they don't have much of a marketing budget. A Kickstarter campaign last summer to raise $20,000 fell flat. "It's a lot harder to sell people on an untested app than it is on music," Shekey said.

They've already landed a favorable write-up at Forbes.com, however. They're calling this week's release a "soft launch" to help build buzz. They plan to add several functions to the app in the coming months, including a tuning device and an easy link to Dropbox (a popular file-sharing platform). Hum apps for iPads and Android phones are also on the horizon.

The duo's initial investment would have been much more, but they were able to do a lot of the coding and nerdy work themselves. They did hire one outsider to handle the hardest of the technical operations, a Chicagoan named Ellen Shapiro — also a songwriter, they made sure to note.

"For us, it's so important to get real songwriters talking about it and believing in it first," Kuefler said.

Chris Riemenschneider • 612-673-4658