A hackathon Walkman app uses the iPhone Duo's hinge as its play button

Vidit Bhargava brought a real Walkman to the Bitrig hackathon, because many of the people there would never have seen one ^[11]. "So, when I was looking for ideas for the hackathon, I was looking for physical objects that have a hinge. I noticed how the Walkman's door needed to be opened to insert a cassette, and I thought it would be cool to replicate on the Duo," he told TechCrunch ^[10].

TechCrunch described the app in terms of the Duo's two screens, 7.6 inches inside and 5.4 inches outside ^[8]. For anyone building for the Duo, the useful part is what happens as the phone moves from one screen to the other. In Duo-Man, you open the phone to pick an album and "insert" the tape, and you close it to press play ^[2].

TechCrunch wrote that the Duo "may already have its first killer app. Or at least its most whimsical one!" ^[14]. What exists today is a weekend project that placed second ^[3] and a post on X that passed 1.8 million views and nearly 10,000 likes ^[12]. Buyers cannot try it yet, because Duo pre-orders do not open until later in October ^[9]. So the evidence is one developer's prototype for Apple's first foldable ^{[1] [16]}. It shows the hinge can work as a control, and the sources describe no other developers building the same way.

TechCrunch links the app to younger buyers seeking out cassette tapes and flip phones ^[17]. The motion itself comes from an object that many of the people in Bhargava's hackathon room had never held ^[11]. Opening a lid to put something inside is familiar well beyond cassette players, and I think that familiarity is why the gesture needs no tutorial.

The hard case is the ordinary close. People fold a phone shut to put it away. An app that plays on close has to work out what each fold meant. For a music player, an album starting in a pocket is a small annoyance. In a camera or a messaging app, the same fold could do something the user never asked for.

The roadmap is still modest. The shipping version is due to support Apple Music and local files, plus an Apple Pencil gesture to "roll" the cassette loop ^[5]. Bhargava said on X that fast-forward and rewind will work much as they did on the original ^[6]. Spotify support "may be added further down the road," in TechCrunch's words ^[7]. He has shipped apps before, including the dictionary LookUp and Movie Buzz ^[15], and he said he will now release this one as an actual app ^[4].

For a team deciding whether folding should be an input in its Duo app, two questions sort most cases. The first is whether the fold copies a motion users already know from a door or a lid. The second is whether an accidental fold is harmless in that app. If the motion is familiar and a stray fold does no harm, make the gesture the default, as Duo-Man does. If the motion is familiar but a stray fold is costly, put the gesture behind a setting. If the motion is invented and a stray fold is harmless, offer it as a shortcut next to a button. If the motion is invented and a stray fold is costly, folding should only change the layout. After launch, a team can compare the share of sessions started by a fold in week four with the share in week one.