Resample to 44.1 kHz
Drop an audio file and export it at 44.1 kHz as a WAV. Files recorded higher are filtered and resampled down; files already at or below the rate are left alone.
The rate music ships at
CD audio is 44.1 kHz, and music streaming platforms deliver at the same rate. A track mixed at 48 kHz or higher has to arrive there eventually, and doing the conversion yourself means it happens once with a known resampler rather than inside an encoder you cannot see.
Where the odd number comes from
Early digital masters were stored on video tape, because nothing else could hold the data rate. The number of usable lines per frame multiplied by the frame rate gave 44,100 samples per second under both NTSC and PAL. CD inherited it, and it has stayed ever since.
48 to 44.1 is not a clean ratio
48000 / 44100 reduces to 160 / 147. There is no simple relationship between the two grids, so almost every output sample falls between input samples and has to be interpolated. The error is small and well below audibility with a good resampler, but it is real, and it accumulates if you convert back and forth repeatedly.
Convert once, at the end of the work, in the direction the delivery format needs.
The 22.05 kHz ceiling
Half the sample rate is the highest frequency the file can hold. Anything above 22.05 kHz is filtered out before the rate drops, which prevents it folding back into the audible band as an aliased tone. Human hearing tops out well below that limit.
Other delivery rates
Audio travelling with video wants 48 kHz. Speech recognition usually wants 16 kHz. For mono downmixing or a different output format, use the full Sample Rate Converter.