There are different ways to include audio files into your Webflow project. You cannot host or upload the mp3 file into your Webflow account but many domain provider offer external hosting as well. It's even possible to host it via your Dropbox account.
Based on the Green Audio Player including the support for multiple audio players on a single page. The player looks the same in each browser. Styling via CSS possible. https://github.com/greghub/green-audio-player
Easy to embed. With the free plan you are allowed to upload mp3 files with a total time of 3 hours. https://checkout.soundcloud.com/pro