Do you get sent folders full of audio files from other recordists to mix? If you do, I'll bet there are frequently stereo audio files in there that are actually mono. Apple's Logic DAW seems to be the worst culprit, organizing sessions in an "always stereo" way that confounds less experienced track exporters and leads to so many mono-as-stereo files. I've been putting NUGEN Audio's SigMod [Tape Op #127] on my master bus with a left channel polarity flip and mono sum on; then I import all the audio tracks, solo the stereo ones, and see if the track cancels itself out. If it does, I'll split the track into mono and then delete or hide the stereo track and one mono track. What a pain. Why would I go to all this trouble? In Avid's Pro Tools, we can just use their DownMixer plug-in to make a stereo track act mono, but we are still processing twice the information, and the file size is still double what we need – yes, I know this sort of grandpa-style worry matters less and less as computers get more powerful, but here's the real reason it matters to me – I am constantly panning tracks and looking for space in a mix, so a stereo file that is not stereo messes up my flow, and adding a plug-in to a stereo file to undo it seems pretty backwards.
So, here's MonoMate. It's a very specific app (not plug-in) that will check all the audio in a folder for stereo tracks that are really mono and convert them to mono. There's a previous app by Soundizers called StereoMonoizer, but it still hasn't migrated to Apple Silicon. Thomas Dulin wanted something quick and affordable to sort this problem out; thus, MonoMate was born. (Note that MonoMate is macOS 14.0 or later only at this point.)
It's so easy. Select the audio files folder, and it loads them in – note that MonoMate will load all files from subfolders as well. Default settings add an output suffix of "_mono" to the newly made mono files (you can choose anything or nothing for this). The original "not really" stereo tracks will be moved to a "backup" folder within your original folder, or they can be automatically deleted or left in place. A bar at the bottom displays the number of Total Files, Dual Mono files, True Stereo files, and the "Potential Savings" of storage space. Smart. The interface also displays every file’s bit depth, sample rate, length, size, and Status (Already Mono, Dual Mono, True Stereo, etc.). This can be handy info if you've been given files of differing sample rates and bit depths, and good info for setting up your session in any case. MonoMate also looks for and converts files in which one side is complete silence, or left and right have inverted polarity, or even the dreaded left and right are both silent (bad export or mistake?).
I asked Thomas if the app would eventually be able to spot "panned" tracks, like when someone exports a stereo rack tom that was actually a mono signal panned partially to the right or left. Within weeks, v1.2 came out, and it finds "panned mono" tracks, notes the pan percentage, and (if you choose to convert these) will choose the louder side as the mono track. I'd love a feature that identifies all those amp sim plug-in tracks and virtual instruments where the only stereo content is a slight tinge of fake reverb that doesn't matter to the core sound (though I understand this is subjective!).
I've noticed that a lot of my Tape Op reviews say, "This will speed up my mixing process," and many times these new apps and plug-ins certainly do help me work faster. But I can guarantee you that MonoMate will speed up the beginning of all my mix sessions (unless I tracked it myself, ha ha), as almost everything I've received for mixing over the last 20 years has had files that need to be checked and fixed. Less guesswork, less searching, less splitting to mono and deleting, and more time actually mixing. Thank you, MonoMate!