Is your smartphone ready for radio?

Remember transistor radios? The kind that fit into a shirt pocket and ran on a 9-volt battery? No, they’re not obsolete. You may have used one of them today, to make a phone call.

Most smartphones made today have plain old FM radios built inside, the kind that can tune in music stations, local news bulletins, and Patriots games. However, many smartphone users don’t use them, and millions more can’t, because the radio is often disabled. Apple’s iPhones, for example, have their FM receivers turned off.

With such a large audience out of reach, several stalwarts of the industry — the National Association of Broadcasters, National Public Radio, and American Public Media — have launched a lobbying campaign to get those radios switched on. They’ve also come up with an app, NextRadio, that arranges all your local FM stations in a handy menu, displays what’s playing on each, and let’s you tune to one with a simple tap of the screen. You can even use it to buy that new song you can’t get out of your head.

However, the app only works on FM-capable phones running Google Inc.’s Android operating system.

How did an FM radio get into your smartphone? Phone makers found that adding the feature costs almost nothing. Outside the United States, customers love it, especially in developing countries where FM is a zero-cost alternative to streaming digital music. FM radio is also an excellent way to get news updates during disasters, when cell systems are often overloaded. The Federal Emergency Management Agency has recommended FM-capable smartphones for keeping informed during a crisis.

But with most smartphones in the United States, the FM feature is switched off, with one major exception — Sprint Corp., which did a deal in 2013 with Emmis Communications, the radio and publishing conglomerate that makes NextRadio. You can listen to FM on about two dozen Sprint Android phones from HTC, LG, and Samsung. In exchange, Sprint gets a cut of the revenue generated by ads that appear in the NextRadio app.

But the other three majors — AT&T, Verizon Wireless, and T-Mobile — only offer a few phone models with working FM radios. For instance, the latest HTC One phones offer FM, no matter which carrier you use. Conversely, the FM radio on a Samsung Galaxy S5 works for customers of Sprint, but not for those of the other carriers.

The FM chips in Apple Inc.’s iPhones don’t work, not even the ones sold by Sprint. I asked Apple why not, but got no reply. I also asked AT&T, T-Mobile, and Verizon why they don’t activate the FM radios. None would tell me. The cellular industry trade association, CTIA, was just as unhelpful.

One guess: People with FM radios will stream less digital music and download fewer songs, perhaps eroding cell company revenues.

But San Diego radio consultant Mark Ramsey isn’t buying that explanation,on the grounds that listeners aren’t really “saving” anything by using their phone radios.

He estimates you’d have to stream music for four hours a day, every day, to burn through the typical monthly data quota. Besides, most American music streamers usually fall back on their home or office Wi-Fi service, rather than their cell data plans.

Instead, Ramsey thinks traditional radio companies are pushing NextRadio in a desperate bid to stay relevant in the cellular age.

Well, maybe. But as desperate bids go, it’s not bad. Even though I’m an AT&T subscriber, I was able to use NextRadio because I own an HTC One phone, with a working FM chip inside. As with all FM-capable phones, you need to plug in a headphone; its wire acts as the radio’s antenna. There is also an option for playing songs through the phone’s speakers instead.

My phone already had a primitive FM radio app that let me flip through local frequencies and lock in some preset favorites. The app also displays song titles on the phone’s screen.

NextRadio offers quite a bit more.

It uses the phone’s data network to download album cover photos and titles. These appear on icons representing all local stations. At a glance, you can see which songs are playing all along the FM dial. Just tap an icon to tune in.

Because it’s FM radio, the music starts instantly, without the brief delay you get with digital streams. And if you’d like to purchase a recording, tap the screen and you’re taken to the Google Play online store, which offers millions of tunes for sale, usually priced at $1.29 per song.

NextRadio is FM radio made smarter, but can it compete with the Internet’s deep and diverse audio streams? Probably not. But until AT&T, T-Mobile, and Verizon end their irrational FM lockdown, most of us will never get to choose.