I’ve been using the sci-fi subscription on my iphone for a couple months now. I don’t own a laptop so I use Syrinscape exclusively with my phone, the only problem is I can’t use another app or exit Syrinscape without it stopping. I cant tell you how irritating it is when the players around the table are on the edge of their seats and suddenly the environment sounds stop because I needed to check the map or look up stats etc.
Sorry for the copy and paste, but there’s a good answer on our FAQ. 
Syrinscape uses the super powerful Unity engine for its 3D surround audio. At the moment that’s what’s stopping it from going into the background. Think of Syrinscape more as a fully fledged sequencer (like Garage Band = stops in the background) than a music player playing a single mp3! Often Syrinscape is playing back 20 or more sample simultaneously, each with dynamic positioning, reverb and even doppler effect. Performance and responsiveness becomes a BIG issue when processes go to low power mode, and there’s issues with keeping Unity running and not destroying the rest of the Tablets system, thus Unity (and hence Syrinscape) pauses atm. I have actually found it is best to have Syrinscape sitting open on the table in front of me so I can change Sounds with just a single touch. Just make sure you keep the screen brightness low-ish so as not to drain your battery.
ALSO: Remember you can sign in as you on up to three devices at once, so you might get one of your players to bring a tablet to devote to Syrinscape for the game, with the bonus that they will get to keep the sounds when they are home too. Just make sure you leave a chunk of time to download necessary content.
Does that all make sense?
That said, should it become possible to keep Syrinscape running in the background at some time in the future, be assured, we will DEFINITELY go for it! It’s something I would like too!
Makes sense?