If I understand you correctly, you wanna configure your Rpi as a USB audio gadget. I have never done this, yet. However, you can have a look here (pay close attention to the Raspberry Pi Zero OTG Mode insert). In this case, you wanna configure your Rpi to use the g_audio module and turn it into a USB audio gadget for use on your computer. You will do this by editing the /boot/config.txt and /boot/cmdline.txt files using a text editor of your choice. For the /boot/config.txt file, you need to add dtoverlay=dwc2 on a new line. For the /boot/cmdline.txt file, add modules-load=dwc2,g_ether after rootwait and it will something like shown below. Since I haven't done this as of this writing, I can't confirm this will work or not. So, you are advised to backup both your /boot/config.txt and /boot/cmdline.txt files in case this approach does not work.
dwc_otg.lpm_enable=0 console=serial0,115200 console=tty1
root=/dev/mmcblk0p2 rootfstype=ext4 elevator=deadline fsck.repair=yes