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If I'm understanding your question correctly, it sounds like you want to bypass using a payment merchant like Paypal or even Etsy, Shopify, etc? If you want to make money, you will need a way to collect the money from people, unless you will be doing a cash transaction in person. You can use venmo or Square to accept online payments without setting up an online store. You can try apps like Depop.
You can share the individual song by grabbing the Embed code in Spotify. To do this, find the song in Spotify and click on the ellipsis, aka the three dots (...) to display more options. Select Share --> Copy Embed Code and place this code where you want the song to display on your website. You will also see other options available. If you choose "Song Link" it will open the song in Spotify.
Another option is to create a playlist of the songs you want to suggest and embed the entire playlist.
If you aren't restricted to using Spotify, you can also embed songs from YouTube or create a YouTube playlist of the songs you want to share.
Hope this helps!