Here are some useful articles I use for quick reference:

Using Equalisation – “Paul White and Mike Senior explain how to get the best practical results from equalisation by understanding the true frequency ranges of most instruments and voices.”

Compression Made Easy – “Getting precisely the results you want from compressors can often be the key to a tight, modern-sounding mix. We explain what the controls are designed to achieve and how they relate to what you hear.

Vocal Recording and Production Masterclass – “Everyone knows how much a classy vocal sound can add to any recording, but achieving this in the studio can seem something of a black art, so this month we demystify the recording, processing, and mixing techniques required to produce professional results.”

Parallel Compression – A short article explaining Parallel Compression


Some very useful links:

Frequencies of Musical Notes – Simply a list of notes and their associated frequencies and wavelengths

Ricci Adams’ Music Theory – An easy to use and extremely helpful site for brushing up on your music theory