iPhone Audio Editing: Monle and Hindenburg Mobile

Hindenburg Field Recorder

Intro from Jay Allison: For the past ten years, Transom has sought out and tested the best tools for audio journalists and producers. We’ve reviewed venerable, hardy cassette recorders and the latest, tiniest digital machines. A new category of tools is emerging: audio editing and transmitting via cell phone. Jeff Towne has the latest on two amazing little apps for the iPhone - Monle from American Public Media, and Hindenburg Mobile from Nsaka -complete with screen shots, audio samples, and Jeff’s careful testing.

from Jeff Towne

HindenburgPlayIt started as an Apple marketing slogan, then morphed into a pop-culture cliché: There’s an App for that. The idea that you can do pretty much anything on an iPhone has become an overused joke, but as we covered in a previous column, with the addition of some hardware, the iPhone CAN indeed become a viable field recorder, capturing good-sounding audio to its internal memory. Now, with the release of some new, affordable apps, it’s even possible to edit that audio directly on the iPhone, and to use its WIFI or 3G connections to send that edited audio to remote FTP sites, back to a host computer, or even as an email attachment. One app even provides multitrack layering of soundfiles, allowing the user to place edited sounds along a timeline, overlap sounds, and mix these elements down to a mono or stereo file, all in the iPhone.

Of course there are compromises: the small screen is a frustrating limitation, as is the size of the iPhone’s memory; the touchscreen gestures used to manipulate the audio are clever, even elegant, but often less efficient than an old-fashioned keyboard and mouse; ending up with consistent audio levels can be a challenge. But the fact that one can make these kinds of manipulations at all, and end up with results that sound plausibly useable on the radio or podcasts, is pretty amazing.

The Apps we’ll be discussing are Monle, from American Public Media, and Hindenburg Mobile, from Nsaka. Both programs were created by radio people, for radio people, with an eye toward keeping things simple, acknowledging the reality that reporters and independent producers are increasingly expected to do everything in a production themselves, without the intervention of an audio engineer. These tools can also empower beginning producers who may not be able to afford a dedicated filed recorder, a standard computer, and editing software. An iPhone isn’t cheap, but if one already HAS one, the apps are very affordable: $10 for Monle, $30 for Hindenburg Mobile.

An iPhone and these apps are not real substitutes for a desktop computer or laptop with ProTools, Audition, Audacity, or some other full-fledged editing program. It would be impractical, maybe impossible, to do a long, complex production with these tools. But the ability to edit and mix simple, short pieces, and to file them from the field, is very powerful.

The two programs are very different, and have their own strengths and weaknesses, but both allow sophisticated manipulation of audio recorded or imported into the iPhone. Both Apps have very good tutorials explaining their features and how to use them, so there’s no need to repeat all the details here.

The basic overview is:


  • Single-track (Stereo or mono, or a mix of the two)
  • Trim and fade in and out of sound clips; cut/copy/paste/clear sections of larger soundfiles
  • Volume automation within clips
  • Clips can overlap
  • Good input and output metering
  • Location and photo tagging of sessions
  • Ability to import .wav files into the iPhone from an external computer running a companion program via WIFI
  • Flexible output of sessions via FTP, email, or integration with companion desktop program.

Hindenburg Tutorials: http://www.nsaka.com/screencasts

Monle-overlapVolume manipulations are similar: in Monle, just drag up or down on a clip with two fingers. The faint white volume line is hard to see, but it’s useable. In Hindenburg, one selects the segment by tapping, then dragging the top line of the segment up or down, which makes the volume adjustment easy to see. Hindenburg Mobile also has a playback level meter, which makes deciding on a volume much easier. Monle currently lacks a playback meter, so absolute levels are a guess.

HindenburgSelectThe desktop program offers some slick integration with the mobile app: clicking on Send to Hindenburg automatically opens soundfiles from the iPhone in the desktop app, as long as both devices are connected to the same WIFI network, the program is booted on both machines, Bonjour is on, and the computer is selected in the Hindenburg Mobile prefs. The documentation indicates that one can send audio in the other direction as well, from the desktop app to the iPhone, but I haven’t been able to do that yet…

HindenburgCompAdding to the power of the app is the simple, yet effective, compressor built into the playback flow. It’s one dial, for either more or less compression, with a helpful gain-reduction meter. It’s an upward compressor, a mode that adds make-up gain automatically, so that average levels go up as more compression is applied. As is always the case with compressors, there are no hard-and-fast rules about what works and what doesn’t, it’s very dependent on the nature of the sound being treated. So, experimentation is the best path, try turning the dial up and see if it sounds better. Stop when it starts sounding worse, and back the dial off a little.

Listen to “Hindenburg Sample Audio”
Listen to “Hindenburg Compressor”

Monle-overlapUsing a Blue Mikey to record into Monle, I asked a couple of friends, one visiting from England, what they thought of the American craft beers they’d been sampling at a Philadelphia gastropub. We were on the street outside the place, so there’s considerable ambient background sound, including, oddly, someone playing a harmonica. Fading the edges of the clips helped ease the transitions between edits, and between voices.

Listen to “Street Interview”

But what if we felt that this conversation didn’t sound sufficiently pubby? We could layer-in some ambience from inside the bar to make it sound like were still inside.

Listen to “Street Interview with Ambience”

Monle-filemgmtOnce all the elements are in place, simply press the disc icon at the bottom of the screen to go to the file management area, and choose Mix. Be sure that the entire session is visible before pressing Mix, if soundfiles are off-screen, they will get chopped-off.

The one downside is that I found this version of Monle to be a little crash-prone, especially when stacking-up several tracks, or making separations in long soundfiles. But the app makes it easy to save and name sessions, so it should be fairly easy to get back to where you were, if you’re careful to save often.

Monle-sharing2Outputting audio from Monle is very flexible. My favorite way of moving files is to connect to another computer that’s on the same network as the iPhone’s WIFI connection. Monle will display a URL that can be entered into any web browser. Entering that address will bring up a file list that includes all of the elements, as well as mixed files. That page also offers an upload utility, for moving wav files into the library, for use in Monle sessions. At this point, only wav files are allowed, but it’s a good policy to keep all one’s mix elements at full quality anyway.

There is NOT currently any elegant way to move audio from the iPhone’s iTunes library into either one of these audio editors, regardless of the file format, so adding music to a production requires connecting to another computer. But if music soundfiles are transferred to the iPhone before heading out into the field, they can remain in the library, and a multi-layered production can be created entirely in the iPhone.

Monle features a handy audio cut-and-paste function that allows transferring audio out of Monle into other compatible apps on the iPhone. Monle and Hindenburg can’t currently exchange soundfiles, but one can certainly hope for that in the future. Smooth interchange between the two apps, taking advantage of Hindenburg’s more precise editing, and Monle’s multitrack layering, could make for a powerful combination.

Again – neither of these apps will replace a Digital Audio Workstation on a desktop or laptop computer, but for simple productions, especially ones that need to be done quickly, or in a remote location where lugging even a laptop would be impractical, these tools offer a plausible solution. And for iPhone owners, these apps provide an affordable introduction to audio editing, which may be useful for aspiring audio producers with limited budgets.

It’s almost certain that these apps will add more features, and that new programs will join them, so tomorrow, who knows what will be possible? It’s not clear whether either of these programs will be ported to other platforms, such as Android phones, but it would be surprising if there were not some similar applications written for those formats.

It’s unlikely that we’ll abandon our full-sized computers completely, especially for long-form and complex productions. But for a time-sensitive story in the field? An iPhone might be enough…

Jeff Towne

Jeff Towne

During more than 25 years as a producer of the nationally-syndicated radio program Echoes. Jeff Towne has recorded interviews and musical performances in locations ranging from closets to cathedrals, outdoor stages to professional studios, turning them into radio shows and podcasts. Jeff is also the Tools Editor for Transom.org, a Peabody Award-winning website dedicated to channeling new voices to public media. At Transom, he reviews field recorders, microphones and software, helping both beginning and experienced audio producers choose their tools. In his spare time, Jeff will probably be taking pictures of his lunch in that little restaurant with the strange name that you've been wondering about. 


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  • Flawn Williams


    Need current versions of hardware

    Great to see such an in-depth treatment of these apps. Monle in particular is a brilliant distillation of workflow to get a roughly laid-up piece into the hands of an editor at headquarters quickly.

    To use Monle you need very recent hardware. I was excited when it came out recently, until I saw that my second generation iPod Touch, not much more than a year old, didn’t make the grade. So while the apps are cheap, unless you have the latest and greatest hardware your entry cost may be steep.

  • Dan Epstein


    Monle as Control Surface?

    Thanks for the in-depth review.

    After playing around with Monle I realized that I’d really like it to function as a control surface for my backup/run-and-gun recorder, a Zoom H4.

    Overall I found Monle easy to use although I did have some crashes with longer files. I did have difficulty grabbing and manipulating the volume line. And I’d really like to see some kind of metering.

  • benjamenwalker


    so great to have this

    thanks transom!

  • John Bonell




    You mentioned using a Blue Mikey. Does that work with an iPhone the same way? And how would you compare that to other microphones and the built-in mic on the iPhone?


  • John Bonell



    Please forgive my last post. Had I just looked at your next article down the list I would have found your review of the Blue Microphone Mikey.

    As mentioned in your Hindenburg review, I’m using my Beyerdynamic MCE 58 microphone with my iPhone. I wonder how it compares to the Blue Mikey.


  • Jeff Towne



    John – yes, the Blue Mikey works with the iPhone, BUT!!! At the time of this writing the current model does NOT work with the iPhone 4. It works fine with the 3Gs. That’s what those audio clips above were recorded on.

    Check this list before getting a Blue Mikey:


    They’re supposedly working on a digital version that will work with newer Apple devices, but I have no idea when that might be available.

  • Larry




    Since some time has passed since this article was written, I’m wondering if you have an interest in updating reviews on current software.

    I came across this link for what the manufacturer calls Pro Audio to Go. I’m wondering how good it really is.

    Also since I use an Android phone, are there Android equivalents?

    Since my phone is always with me, it would be nice to be also to record sound WELL with it.

    And, now for something mostly different.

    I just ordered a flash memory recorder to connect to my Sound Devices 302 mixer, I’m wondering if any particular device might work with the tape out on the 302 to get the best quality sound recording, without buying a $2000 Sound Devices recorder. Since the 302 preamps are good, I’m assuming the analog to digital conversion is the important hardware needed. I could even use a recorder without any mics, since I have a dozen that plug into the 302.

  • j-dog



    Just wondering if there’ve been any new developments with recording phone calls on the iPhone. I do a lot of interviews with the iPhone, and want to record them for shows I’m producing. Any thoughts? Thanks!

  • Charles Wilson (@charlesw)



    I don’t have an easy method of recording calls for interview. I do know the Uber Conference service (free voice conferencing for up to 10 people) offers call recording. I’m unsure on the quality of the call.

  • Jim Park



    Jeff, responding to this old post, you note that there is no elegant way to get audio files off an iPhone. Try iExplorer. It’s a third-part app that opens up access to the iPhone in a way iTunes does not. I use it to grab photos and audio files in about three clicks. The files are archived and really easy to find and download.

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