Are there any other older versions of Linein that support mac os 9 (or older) or other programs that do the same job? I have found only LineIn version 2.03 which is only for mac os X. (LineIn is a simple application for OS X to enable the soft playthru of audio from input devices. In simpler terms, you can use LineIn to play sound coming in through a microphone or any other device plugged in to your Sound In port, just as was once available with OS 9's "Play input through output device" option.)