Ah, the old "how many is too much" problem. You're not alone Dan60, I had a similar problem with my developmental game, Blox. During a level testing session, I had the rapid-fire powerup enabled, which allowed me to shoot about 20 or more lasers a second, with a laser sound for each shot. Needless to say, it sounded more like one continuous sound than individual shots. Moreover, if too many sounds played at once, the background music cut off! I included a little bit of code to restart the BGM if it stopped, so that was the end of that. Bottom line, it is definitely possible to have too many sounds playing at once. Looking at your code, it doesn't seem like you should have that problem, but it also depends on how long the sounds are, and how frequently they play. I'm no Blitz sound expert, so I can't help you much more, but you might want to contact Support, or if you can, Mark Sibly (Blitz's creator) to see if you can get any further help.
Good luck!
Good luck!