On GNU/Linux, by default, Harmony can only play audio files with these specifications:
Format: Waveform Audio File (.wav)
Sample rate: 22 050 Hz
Sample size: 16 bits
Channel mode: Stereo
If FFmpeg is installed on your system, Harmony will use it to transcode other audio formats into this format on the fly. However, FFmpeg comes bundled with patented algorithms such as encoders and decoders, the unlicensed use of which may contravene intellectual property laws in your jurisdiction. Hence, if you use Harmony on GNU/Linux, it is recommended to transcode your audio in the format specified above using third-party software before importing it to your Harmony scene.