I have a similar script as follows
(sleep 5m; echo "set_property volume 85 > "fifo_file")&
mplayer -volume 95 -quiet -slave -input file="fifo_file" song1 song2 song3
This makes the current song change volume to 85 after the 5 minute sleep period, but any songs after that revert to 95.
I want to keep it at volume 85 until the mplayer command completes but start at 95 until changed.
Is this possible?