Audio Joiner

Joining audio files sounds simple, but mismatched volumes and abrupt cuts make the result sound amateur. FreePDF’s audio joiner merges any number of tracks in the order you choose, can blend them with a smooth 2- or 5-second crossfade or insert a short silence, and can even out loudness so one quiet recording does not disappear. It decodes and encodes everything inside your browser – nothing is uploaded, and there are no watermarks or length limits.

Common uses

• Combine parts of a podcast or interview recorded separately.
• Make a continuous mix or playlist from several songs.
• Join voice memos or lecture recordings into one file.
• Stitch an intro, main content and outro together.
• Create a workout or meditation track with gaps between sections.

Tips for best results

• Use crossfades for music and silence gaps for speech.
• Turn on loudness matching when combining recordings from different devices.
• Export WAV if you will keep editing; MP3 for sharing.
• Trim each clip first with the audio cutter if it has long silences.
• Keep the sample rate in mind: everything is resampled to one rate automatically.

How the joining works

Every file is decoded into uncompressed samples, converted to a common sample rate and channel layout, and placed one after another on a single timeline. For a crossfade, the end of one track fades out while the start of the next fades in, overlapping for the chosen time. For gaps, true digital silence is inserted. The finished timeline is then encoded once, so quality is lost only a single time even when you join many files.

Evening out loudness

Recordings made on different phones or microphones often differ greatly in volume. With loudness matching on, the joiner measures each track’s average level (RMS) and adjusts it towards a common target, while preventing clipping. It is a gentle, practical normalisation rather than full broadcast mastering, but it removes the jarring jumps that make listeners reach for the volume control.

MP3 or WAV?

MP3 files are small and universally playable, so they are best for podcasts, sharing and phones. 192 kbps is a good default; 320 kbps for music you care about; 128 kbps is fine for speech. WAV is uncompressed and lossless, ideal for further editing, but files are around 10 MB per stereo minute. You can always join to WAV first and convert to MP3 later with the audio converter.