Hi Audacity, How do I make it sound like 1999 recording?
Audacity Version: 3.7.3
Try using the Telephone preset in the Equalizer effect. There are other presets you can try as well.
I’m going by memory here, so you might have to poke around to actually find it.
The graphic equalizer is pretty easy to experiment with: Effect → EQ and Filters → Graphic EQ.
The Filter Curve EQ is more flexible/powerful, but not as easy to play around with. It has presets for AM Radio, Telephone, Treble Cut, and Walkie-talkie.
…We had digital recording in 1999. 
In the mid-to-late 60’s pro analog recordings were getting very good, and certainly not “muffled”. (At home the best we had were vinyl records which had more limitations, but by 1999 we had CDs.)
In terms of recording quality, there is no difference between 1985 and 2025.
PLEASE STOP asking virtually the same question over and over without explaining what you actually mean.
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Old recordings aren’t just about limited frequency - they also have specific glitches and artifacts, similar to JPEG scaling issues. Simply reducing frequencies won’t replicate these effects. Listen to 1990s recordings to identify the artifacts you need to implement. The best option is to use equipment from that era, because even if you 1) cut frequencies to 100–15000 Hz 2) compress dynamics 3) even mimic tape pitch fluctuations, replicating side effects like bass distortions might be impossible without authentic gear