Here is a short guide on how to build QEMU to run Mac OS 9 with working audio. These instructions work for MacOS High Sierra as the host OS, although with some tweaking they may run under Linux/Windows. You should be comfortable compiling software from source before attempting.
Adapted from instructions from Cat_7
You may need to install XCode and/or the XCode command line tools. If you do not have them, then this process may prompt you to install them (MacOS will do that).