On second look, I was strace-ing for reads, too. The command line I used was:

strace -p28 -p30 -p31 -p32 -p33 -p34 -p35 -e open,read,wrrite,lseek,close -s 1024

I just picked a few of the player processes until I found the one that does the hda3 writes. No reads involved, apparently, so those unnecessary lseeks do look kinda funny.