To merge two songs, put the song transition at the end of a phrase, usually bar 8 or bar 16, and overlap a fade there. Combine two songs that already share a compatible key, a tempo that matches or sits at half or double time, and a similar loudness. The Audio Joiner keeps each file's tempo and pitch, so a musical mismatch has to be solved before the fade, or the join carries it through.
Combine two songs that already agree
Run both files through the Key & BPM Finder before you trim anything, and only combine recordings you have the right to use together.
Choose one file, then Analyze Key & BPM, and write the key and BPM down before you load the other file. The finder reads key, BPM, and Camelot in the browser. A shared Camelot code, a neighbor on the Compatible line, or the relative major or minor is a reasonable pair to blend. Half-time and double-time BPM are on the same card, so a song at 70 and a song at 140 read as the same pulse at two speeds. These figures are estimates. A low-confidence key, or a track that changes tempo, can look tidy on the card and still fight once the fade starts.
If the codes sit far apart, or the tempos are not the same, half, or double, pick another song, or generate one that already fits. A short fade on a quiet ending is the fallback, covered with the fades below.
Match loudness before the fade
Loudness is the jump that remains after key and tempo already agree. Past each fade, the clip plays at the level it arrived with, because the joiner's gain only draws the fade. A quiet verse running into a loud chorus from the other file lands as a step in the middle of the overlap.
Pick two tracks that already sit at a similar loudness, and confirm that by playing them back to back at the same playback volume. When one is obviously louder, match them in a free editor first. In Audacity, select the audio and open Effect, then Volume and compression, then Normalize to line up the peaks, or Loudness Normalization with the same target on each file when you care how loud they sound. A longer fade can mask a small jump that remains, by spreading it across the overlap. A large difference still belongs in the editor, before you touch the fade.
Put the transition at the end of a phrase
The cleanest place for a song transition is the end of a phrase. In a typical 4/4 song that is the end of bar 8 or bar 16, where a vocal line finishes, a cadence lands, or a fill hands the tune to the next section. Joining in the middle of a word, or on a random quiet spot inside a phrase, is the common mistake. The fade is then crossfading two sentences, and no curve makes that feel like one piece.
Find it by ear before you trust a timestamp. Start on a downbeat, the pulse where a nod would land, and count bars of four beats. Stop at 8 or at 16, and listen for the line to end. You want the last syllable, the cadence, or the fill, not merely a dip in volume while the singer is still in the middle of a line. The second song should enter on its own downbeat.
The waveform usually agrees with that count. Look for an energy drop after a short burst, which is often the fill, then a lower stretch or a small gap before the next section's peaks jump back up. Trim the first clip so it ends on that drop, and trim the second so it starts on the new section's downbeat. The fade then overlaps the handoff.
Use the BPM to estimate where those bars land, then listen to confirm. For a song in 4/4, one bar lasts 4 × 60 / BPM seconds, because a bar is four beats and each beat is 60 / BPM seconds. At 120 BPM a bar is 2 seconds, so bar 8 ends 16 seconds after the downbeat you counted from, and bar 16 ends at 32 seconds. At 96 BPM a bar is 2.5 seconds, bar 8 is 20 seconds, and bar 16 is 40 seconds. If the file opens with a pickup or a fade-in, start the count at the first real downbeat, not at time zero, or the arithmetic will point at the wrong bar.
That formula assumes four beats to the bar. When the phrase is clearly in three, you are still hunting the end of the 8th or 16th bar, but the seconds change with the meter, so the ear and the waveform outrank the 4/4 sum. The finder supplies the BPM. Marking the bar, and choosing where the join sits, is yours to do.
Set the fade and export
Add both songs and drag them into order. Files from your computer are joined in the browser. That path asks for no account and no credits. From My Music, for a track already in your library, asks you to sign in. Trim the waveform edges so the outgoing clip ends on the phrase and the incoming clip starts on the downbeat you chose.
Leave Trim silence on unless a quiet intro or a long decay is part of the music you want to keep. It clears dead air only where the clips meet, and it leaves the opening of the first track and the ending of the last track in place.
Set Fade out on the outgoing clip and Fade in on the incoming one. On a two-song join those inner edges start at 4 seconds, which is a fair length when key, tempo, and loudness already agree. The overlap uses the shorter of the two fades, so lengthening only one side does less than it looks. Each fade runs from 0 to 10 seconds, and a very short clip stops at half its playable length even if you ask for more. Lengthen both sides, up to that 10 second cap, when a quiet ending runs into a quiet intro. Shorten them, or set them to 0, when the downbeats fight and you would rather cut on the pause.
The join is an overlap, and a fade of 0 cuts on that phrase ending. Nothing on the page inserts a silence between the songs. The start of the first song and the end of the second stay unfaded unless you add a fade there yourself.
Play each clip to hear its trim and its own fade, then Download. Export as MP3, WAV, or FLAC. MP3 is the default. The same joiner is what the meditation music guide uses when a long bed is many short pieces joined in one pass.
When the join still clashes
Shorten the fade and land it on the quieter ending, or choose another song whose Camelot code is on the Compatible line. You can also make a short bridge that already matches the first track. The AI Music Generator writes that bridge from a description. Lining the two files up in time stays in the joiner.