Cassette Culture is a past time of my childhood and I'm very fortunate to be born when I was because I got to witness certain movements and events that happen in the world and in the music world in general, I never understood why things changed when Tapes fell out of favour for CDr's. I reckon you can do the same things that tape culture did with CDr's and MP3's and you can do the Cassette Releases and CDr's releases for those who don't have a Tape Player, for world wide recognition release everything for free in MP3's releases on the internet and give out your music to internet web-labels and real record labels with the intent to make yourself heard. I imagine that Mail-Art can be done with a Computer and Email dubbing it "EMAIL ART", Music has been involved in mail-art for at least 30 years where people would collaborate with other musicians and make music in steps by sending a foundation to one person and that person builds on the track and sends it back and then the other musician builds upon this and sends it back and then back and forth until the track is finished.....Or one person make a song with midi sequences and then sends it to the other musician who puts sounds to it and then one person sings on the song.
Cassette Culture has been closely related to Music Mail-Art because back in the 1980's there were no blank CDr's or DVD's for use in music, there was just Cassettes to record on, you can use a Cassette to save your synthesizer patches on if you have an old synth with a tape output, then you can make a copy and share it with everyone or make the data into WAV file format and pass it on that way, before there was Tape Outputs to save patches and CV/Gate instead of MIDI.
Back in the 1980's there were some people who shared tapes of just recorded noises to use in music and pass them on to other musicians who made similar music and there became a small community of tape trading and demo scenes with there releases and sound cassettes, you can do that today with MP3's and CDr's or DVD's to share sounds and synth presets as well as music.