.TRM is a proprietary format created by a company called “For The Record”.
They offer an online player at: https://www.fortherecord.com/products/ftrwebplayer/
They also offer a downloadable player called “FTR Player”.
You can download the player here: https://www.fortherecord.com/products/ftr-player/
And you can download the manual here: https://www.fortherecord.com/wp-content/uploads/2018/08/UserGuide-Player-6.2.pdf
According to page 32 of the manual the FTR Player has the option to separate the channels and save as AVI, MP3, PCM, WAV, or WMF (WMA or WMV)
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Recording audio without metering and monitoring is exactly like framing and focusing without looking at the viewfinder.