Combine/merge/mix audio files using PHP

While already have the code/script needed to just combine .wav files into a single output file/track, it concatenates them, end-to-end: //function to handle joining/merging function joinWavs($wavs){ $fields = join('/',array( 'H8ChunkID', 'VChunkSize', 'H8Format', 'H8Subchunk1ID', 'VSubchunk1Size', 'vAudioFormat', 'vNumChannels', 'VSampleRate', 'VByteRate', 'vBlockAlign', 'vBitsPerSample' )); $data = ''; foreach($wavs as $wav){ $fp = fopen($wav,'rb'); $header = fread($fp,36); $info = unpack($fields,$header); // read optional extra stuff if($info['Subchunk1Size'] > 16){ $header .= fread($fp,($info['Subchunk1Size']-16)); } // read SubChunk2ID $header .= fread($fp,4); // read Subchunk2Size $size = unpack('vsize',fread($fp, 4)); $size = $size['size']; // read data $data .= fread($fp,$size); } return $header.pack('V',strlen($data)).$data; }//end of joinWavs function //and here's code to pass an array of file names to the above function, and spit out resulting file $outgoing = joinWavs($arFiles); header("Content-Type: audio/x-wav"); header("Content-Disposition: attachment; filename=dynamic.wav"); header('Content-Transfer-Encoding: binary'); header('Expires: 0'); header('Cache-Control: must-revalidate, post-check=0, pre-check=0'); header('Pragma: public'); header('Content-Length: ' . strlen( $outgoing)); echo $outgoing; Do also have some other code to handle something similar with .MP3 files, but, it's a bit longer/too big to post in a message here, but, either way, issue is would want to specifically mix/combine multiple files into 1 output stream/file, but would need/want to set possibly overlapping start times for the input chunks/tracks in the output track, if that makes sense? Now, aside from trying to do this with something like a call to a command line command on different operating systems - that idea seems to get mentioned quite a bit on the 'net, am just thinking that something like this should be relatively doable/possible using binary streams/data from the source files, etc. - or am I wrong here? Stay well Jacob Kruger Blind Biker Skype: BlindZA '...fate had broken his body, but not his spirit...'