I am interested in what other people have to say about this as well, but yeah i was going to say the same as DRodriguez, you can cut up your own tapes and put them back inside your cassettes to make tape loops. You can do this in different ways to achieve different lengths for your loops. There are a lot of videos on youtube how to do this if you want to see someone take you through it step by step (like this one
https://www.youtube.com/watch?v=hER3s1NPr_U). Also, if you are looking for inconsistencies, warble, or warp, having the tension of the tape not quite match perfectly (which will most likely happen on making your own tape loops anyway at some point) can achieve this. So long as the tape catches and feeds somewhat fluidly through/past the heads, it will do the job. The photo he posted above is another easy way to do a tape loop. If you have the space, you can can use tape stretched out to run through something that will catch it and create tension (in the photo above the second tape machine serves this purpose, but you could use a variety of methods for it depending on your situation). Different tape machines obviously record at different qualities too, and since handheld cheap recorders use internal low quality tiny mics, this is also an easy way to make your sounds 'degraded' or 'aged'.
This is just personal opinion, but i think that one way to really make sounds like this stand out and feel even more alive is to actually focus on creating contrast when you are mixing. I think this is really overlooked. What i mean by this is if all your sounds are really saturated, then together, from a mix standpoint, it will all just sit relative to each other and it won't have a lot of impact. But when you take something that is extremely saturated, and then place that sound next to another part that is pristine and very clear and crisp, this is when in my opinion when things become interesting and bloom and you are able to further your depth and contrast sonically. It obviously doesn't have to be huge or anything, but just something juxtaposed against your warm sounds to further reference and ground just how warm they are with some sort of reference point to ground this fact. But his is just my opinion.
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