You've hit the nail on the head! EQ is absolutely fundamental in music production, often underestimated by beginners but absolutely essential for a professional sound. Here's a breakdown of why, expanding on your points:

Why EQ is Indispensable:

Frequency Spectrum Control:

As you rightly said, EQ allows you to shape the tonal balance of a sound by boosting or cutting specific frequencies. This is crucial for:

Clarity: Removing muddiness in the low-mids, harshness in the highs, or boxiness in the mid-range.

Separation: Creating space for different instruments in the mix by carving out overlapping frequencies.

Balance: Ensuring that no single instrument overwhelms the others.

Corrective vs. Creative EQ:

You accurately pointed out the "corrective" aspect. This includes:

Reducing unwanted resonances or boominess.

Taming harsh frequencies.

Cleaning up rumble or noise.

But EQ is also a powerful creative tool:

Adding brightness and air to vocals.

Boosting the low end for a powerful bass.

Creating dramatic filter sweeps.

Simulating different enviroments with filtering.

Essential for Every Stage:

From individual tracks to the master bus, EQ plays a role in every stage of the mixing process.

It's used to:

Make individual instruments sound their best.

Glue groups of instruments together.

Finalize the overall tonal balance of the mix.

More Than Just an "Effect":

As you said, labeling it simply as an "effect" is misleading. It's a fundamental tone-shaping tool.

It is used in almost every single recording session.

Interactions with other effects:

EQ is often used in combination with compression. For example, you may eq a sound, then compress it, and then eq it again to further shape the sound. This is a very common workflow.

Key EQ Concepts:

Frequency Bands: Understanding the different frequency ranges (lows, low-mids, mids, high-mids, highs) is essential.

EQ Types:

Parametric EQ: Offers precise control over frequency, gain, and bandwidth (Q).

Graphic EQ: Divides the frequency spectrum into fixed bands.

Shelving EQ: Boosts or cuts frequencies above or below a certain point.

High-pass and Low-pass Filters: Remove frequencies below or above a certain point, respectively.

Q (Bandwidth): Controls the width of the frequency range being affected. A narrow Q affects a small range, while a wide Q affects a larger range.

In essence, mastering EQ is crucial for achieving a professional-sounding mix. It's a skill that develops with practice and a keen ear.