Do a lot of comparing of how the mix or track sounds with and without the effect, and let your ears be the judge. If you insert it on a lot of tracks and/or busses and are saturating all of them, it could muddy up your mix, so use it judiciously. They can give you everything from subtle saturation to all-out distortion. Tape emulation plugins are potent tools for mixing. So, use it as a place to start, a place to get ideas for a direction for the settings, but then listen and tweak it to make it work best for your audio track. But remember, even though a preset is programmed for a specific type of source, it’s still somewhat generic. If you want ideas for starting points for your settings, it’s always worthwhile to check the presets that come with the plugin, as there might be one that’s specific to the instrument you’re working with. Tape emulation can sound good on virtually any instrument. Depending on the musical style, it can be a cool effect. If your tape plugin has delay, try dialing in a little slapback (80-150 ms) on the vocal. Using the J37 Level Link feature, the input and output compensate so that you can manage the amount of tape saturation while keeping the plugin's output the same. To handle the volume fluctuations, whether on an individual track or full mix, try automating the tape plugin’s input level, bringing it down during the parts where the signal is too loud. This could also happen when applying tape saturation to a full mix, and is something you should be on the lookout for. You may have the perfect saturation applied on, say, the verse, and then when you get to the chorus, it hits the plugins input louder and causes a distortion that you might not want. Be sure to listen to its effect throughout the entire track, because vocals tend to have a wide dynamic range and can get really loud in a few places. You can fatten up a vocal nicely with a tape plugin.

Waves audio plugins