You can have game data in the first session but that is optional.
If you are looking to make a PS1 game & bleem! disc you do NOT need a dummy audio file in the first session. The actual PS1 game data goes in the first session.
The second session is where you will put bleem. But do NOT binhack 1bleem.bin and the ip.bin. Burn your PS1 game in the first session then after that get the LBA and make an image of the 1bleem.bin file using that LBA.
Excalibur pretty much explained what you need to know here:
http://www.fileforums.com/showthread...5&pagenumber=1