Cut, join and convert audio without surprise quality loss
Plan a clean audio edit, match levels and distinguish extracting an audio stream from re-encoding it to MP3.
Choose the output before editing
MP4 is a container and can hold several kinds of audio. MP3 is an audio encoding format. Extracting an existing audio stream can preserve its encoded bytes when the output container supports that stream; converting it to MP3 usually requires re-encoding. Increasing the bitrate of an already damaged recording does not restore missing detail. Keep the original media.
Make cuts that sound intentional
Open the audio in a suitable editor, such as Audacity, and listen around each cut. Avoid cutting in the middle of a spoken consonant or musical attack. Small fades can reduce clicks at abrupt boundaries. For joined clips, check channel count, sample rate and perceived loudness. A gap, overlap or sudden volume change can be more distracting than the file format itself.
Export a copy and listen again
Keep an editable project separately from the delivery file. Export using settings required by the recipient and listen to the start, every join and the ending. Check that both channels are present and that loud sections do not clip. For speech, intelligibility matters more than selecting the largest bitrate. A voice effect changes the sound but does not guarantee that a speaker becomes unrecognizable.
Know the available route
Daily Desk does not yet include an audio editor or converter. Audacity is a free installed editor; its supported import formats may depend on optional components. Browser editors also vary in codec support and memory limits. Before uploading a long or private recording, test a short non-sensitive sample, confirm where processing happens, and verify the exported file in the app where it will be used.