There are two pieces of feedback that I hear quite a bit related to the audio support in XNA Game Studio Express.
We're investigating what we can do for the first issue, which would obviously help the second issue at the same time. But there is some support for compressing your audio files in the current product, using the XACT tool; it's just not easy to discover. XACT supports ADPCM compression on Windows and XMA compression on the Xbox 360. You can get about 4:1 compression with ADPCM and even better with XMA. So while perhaps not as high as some other encodings, such as WMA, it does offer quite a substantial savings.
So how do you enable compression for your Wavebanks? Let's take a look:
I hope this was helpful for those that didn't know about the ability to compress your audio binaries using XACT. While not as compressed as some other formats, it should provide for smaller game sizes, especially when including audio assets for background music.