FFMPEG : Merging Two Audio Files I am using following command to merge two audio file, which works fine.

ffmpeg -i main.mp3 -filter_complex "amovie=tag.wav:loop=0,asetpts=N/SR/TB[tag]; [0][tag]amix=duration=shortest,volume=2" tag-out.mp3


But what I really need to do is repeat and delay 10 seconds the audio tag depending on the main song length. Also, the main song audio volume lowers while the audio tag plays.

Any ideas/help appreciated. Thanks.
Since you wish to alter effective length of the tag, skip the amovie looping and use the aloop filter after padding the audio to 10s. 

ffmpeg -i main.mp3 -filter_complex "amovie=tag.wav,asetpts=N/SR/TB,apad=whole_dur=10,aloop=-1:1M:0[tag]; [0][tag]amix=duration=shortest,volume=2" -vn tag-out.mp3