Track is too dazzle
When you order professional mixing services happens that engineers tend to make sound too bright. Increasing highs at mixing sure thing can make an audio more attractive, but you shouldn't carry too far. Humans ear way too hypersensitive to sounds between 2 kHz and 5 kHz, and there is a lure to boost these frequencies vicinity to add shimmer to music mixed. Overrating threatens with super flashy and metallic overall mix. How to prevent it: Compromises by EQing is the first solution. If needed an element to make more prominent in a track, while building audio mix mixing studio engineer has to bring in more room while treating other audio tracks. Automated EQ can do a job if you want some sound to stand out at specified spot of a song. Compressor can help if percussive sound way too harsh. Transient designers plug ins will also help to diminish harshness of sound. A pro soundman will always insist that it is all along better to take away it than to boost.
Music mix is too muddy or too flat
The excess of lows can threaten with bad situations both at mixing and CD mastering service. How to prevent it: You should distinguish low frequencies instruments (bass drum, bass) first. Then set a HP filter on rest of tracks to get reed of unnecessary low frequencies. It will make space for the instruments which need lows. After mentioned instruments are particularized, EQ out separate room for them in song mixed. Be very accurate while cutting off lows as their deficiency on vocal track or on the lead instrument will suck life of it. Moreover, by cutting subs (up to 30Hz) you can give more space for bass. Tests are the reply to the fixing of this sort of issues. With time and experience you can develop personal techniques to fix them. To get help with your music mixing please learn my online music mixing and mastering services rates.