what is your favorite music/audio format?

Although I don't use them day-to-day any more, cassette tapes are what I have the most warmth and nostalgia for because they're what I grew up with. Messing around with tapes and making mix-tapes were a big part of my childhood and teenage years, difficult to sell to those who never experienced it but I can't think of any other format that allowed that same level of playfulness and creativity.