When I need to leave to a longer period and I know maybe I will not have internet access and I can't use Google Play Music or any other online solution then I need to put some music onto my phone.
for d in ~/Music/iTunes/iTunes\ Music/Music/*; \ do \ adb push "$d" "/sdcard/Music/`basename $d`"; \ done
Maybe it's too heavy so I made a directory in
~/Music and export bands/albums into it and I run this script there.
for d in *; do adb push "$d" "/sdcard/Music/$d"; done