Playlist.Add multiple Songs

Hello,

I want to add lots of songs (> 300) to the playlist of XBMC via JSON-RPC.
These songs often don't belong to a common album, genre or artist and are in different folders, so I can't use functions like adding by genre-id.

Is there a possibility to add them all at once (via Song-ID or Path)?
Currently I have to send one RPC for each song and this takes really long for this amount of songs.

Thanks a lot for help.