BritChannel is a great way to add some subtle harmonic distortion and analog emulated EQ curves to your signal. The gain is automatically compensated and causes 2nd, 3rd, and 4th order harmonics when set to higher levels, and primarily 3rd order harmonics when in mic mode.
The EQ is 4 band with a highpass, low shelf, mid bell, and high shelf.
Dirty Filter is a simple plugin that includes both high and low pass filters, a variable slope for these filters, a wet/dry dial, an output, and the harmonic distortion dial. The drive function creates odd-ordered harmonics, primarily a 3rd order, somewhat similar to tape and transistor distortion.
Use this plugin on an individual instrument to control its bandwidth and cause some distortion.
It’s rare to see a free plugin pull of multi-band processing, but MGate does it well - you can create up to 6 bands of downward expansion or gating, and reduce the amplitude of the signal whenever it falls below the threshold. Attack and release control the speed of the gating.
A lookahead function can cause more accurate gating and bypass and solo functions are available for each band.
If you’re looking for a quintessential algorithmic reverb sound, one that isn’t realistic but more indicative of over-the-top 80s reverb, Giant Verb is a great addition to your instrument chain. Feedback controls the perceived size of the reverb, while clarity, bandwidth, and pre-warmth control the frequency response.
The modulation section allows for even more unrealistic sounds, so try those out as well.
Chow Tape is arguably the best free tape plugin out there, due to how in-depth the features are, and the oversampling setting at the bottom. The sounds it can create range from slight attenuation of the high end to a completely distorted timbre and truncated frequency response.
For starters, use a high tape speed for hi-fi sounds, and a low-tape speed for lo-fi.
Stage is an easy-to-use stereo imaging plugin that allows you to control both the left and right image, as well as the relationship between the mid and side. Try combining the two different imaging types on an instrument to find a unique placement for it in the image.
The presets available up top will make cycling through the various options easy.
Warmy EP1A is a good emulation of a Pultec EQ, and offers the musical bands you’d expect from the processor. Additionally, this plugin offers oversampling, which is helpful if you’re equalizing high frequencies at a lower sampling rate - although probably won’t do too much given the processor type.
If you want to create some mild distortion, drive the input dial and decrease the output.
Filters outside of an EQ aren’t thought about too much when mixing music, but they can be used for creative effect, especially through automation. Basic Filters allows for some typical and not-so-typical filters like comb and lets you introduce modulation to the filter.
Furthermore, the ADSR of the filter can be controlled.
FreeClip is an easy-to-use plugin with a really smart design, in which the interface actually aligns with the metering and signal level. 6 different clip types allow for different harmonics to form whenever the signal exceeds 0dB, while the oversampling function reduces aliasing distortion.
You can also lower the ceiling to cause clipping more often, and monitor the attenuation to the signal at the bottom.