Few collectible markets have changed more in the past century than music media. With each change in technology, the demand for older music media rises and falls in different ways. What follows is my current grading of the state of the collector markets for the many forms of music media working chronologically from oldest to newest.
Pre-50's (D) - Before the 1950's, music was available on wax cylinders and records compatible with RCA Victor, Edison, and other phonographs. With rare exception, the market for these is currently poor. For every rare jazz/blues record, there are 100's of undesirable symphony, opera, popular vocal, and swing era records. The vast majority one finds are also in poor playing condition, making this a weak music media market now and for the foreseeable future.
Vinyl (A+) - With the discovery of vinyl by new generations of listeners, the market for 33 1/3 and 45 RPM records is better than ever. While many genres remain plentiful and undesirable, others are super hot, including rock, jazz, blues, metal, indie, and early country among others.
Tapes (C-) - Cassette, 8-track and reel-to-reel tapes have small collector markets and the right tape can be worth a lot. However, the supply far exceeds current and probable future demand. Cassettes generate the least interest followed by 8-tracks. Reel-to-reel tapes can be pricey, mostly because these collectors tend to take better care of their media than others.
Compact discs (B-) - The market for CD's is declining rapidly, even though there are still lots of collectors buying them. The advent of streaming services will eventually kill much of this demand, rendering CD's as outmoded and undesirable as cassette tapes.
New Vinyl (B+) - Many records available in stores today in mass market outlets like Walmart and Target are made of a higher quality vinyl than in the 60's, 70's and 80's. They often are made of colored vinyl in limited print runs, but they also carry hefty retail price tags. The future will tell whether these new releases will retain their value. As with any collectible, I recommend buying what you like and not using them as an investment vehicle. Also, check out your local independent record stores and avoid being sucked in by most of these mass market releases.