Just thought to make a thread with collections of those little tricks, that go a long way when you know them and empower you to produce better music, or to produce it faster. You know, we all know a trick or two.
I thought I make a start with some things against tired ears when it comes to bass, I just found enormously useful when trying to learn mixing.
If you have music with deep dull bass notes, and find it difficult to judge them perfectly in key or not, temporarily transpose your bassline up one or two octaves. Much easier to hear now if it is in key or not though it will sound like mickey mouse crap! When tuned to taste, transpose back down again.
when working on bass and especially subbass freqs, I have a butter n4 filter with cutoff at around 150-300 hz on the last pos of master channel. When my ears feel like loosing focus on the bass and everything becoming muddy, I toggle the highpass on, listen a short while to the thinner sounds, then turn it off and am surprised how well I can hear the subbass freqs now! Also to toggle it to lowpass allows one to hear the (sub)bass in isolation.
likewise you can isolate or toggle on/off the highs to reset the ears. or bandpass/notch the mids.
the same filter trick with filter on master also works for judging how you music will sound on systems with little or no bass. for example a butter n8 filter at 200-240 hz will make your tune sound a bit like on a smartphone, butter n4 at 100-200 Hz is like a small stereo with weak bass. Biquad hipass with some reso tuned to 60-110 hz can give impression like a hyped boombox with lack of subbass but boosted/resonating bass. Just take account the reso will boost some, so you will want to lower gain before it hits the speakers. Non-reso filters might also overshoot, but just a little.