The truth is, most musicians simply don't use alto clef, and many music theory beginners don't understand how to read it. I, however, am NOT most musicians, because I speak fluent alto clef. It's actually my native music tongue, because I play the viola, and music written in our normal range is written exclusively in alto clef. Some viola music does include sections in treble clef, but this is usually only when we have notes up in the A string stratosphere for an extended period of time.
Throughout this, I will be relating most things back to violas, and this is mostly because that's the instrument that uses Alto clef the most! A handful of other instruments will sometimes have music written in Alto clef, but as far as I know, the viola is the only mainstream instrument whose home clef is Alto.
So, here are some helpful tips to understanding alto clef!
Also, in case you didn't know, this is an Alto Clef.
It should also be mentioned at this point that if the bottom of the clef does not rest on the bottom line of the staff, it is NOT alto clef. There are many different clefs that use the same symbol, but in a different position. Here's an example of Alto vs. Tenor, which are the two most common clefs that share the symbol.
First off, it's called the C clef for a reason!
I like to say that the Alto clef looks like a deformed 3. With alto clef, the line that touches the middle "point" of the 3 is C. Even more conveniently, this C is actually C4, more commonly referred to as middle C. Everyone makes Alto Clef out to be so hard, but it really makes the most sense. Middle C is actually in the middle of the staff! For the other clefs that use this symbol, middle C is also located on the line that touches the middle point.
Remembering the lines
Remember back in music classes in Elementary school where you learned treble clef, and how the spaces spelled out FACE? That same principle can be applied to the lines of alto clef, starting with the bottom line.
For me, alto clef makes quite a bit of sense, especially for playing as a violist, because when playing viola in first position, you use your odd fingers for notes on lines, and even fingers for notes in spaces. However, if you're trying simply to read the notes for a music theory class, you don't have the advantage of this physical application, so things such as remembering FACE might be more helpful. However, if you read treble clef, I have a much easier way for you to quickly learn to read alto clef. Are you ready?
The Step Rule
This is specifically for people who can already read Treble clef, Bass clef, or both! This is actually the method I used when trying to learn bass clef and re-learn treble clef... and I also might have made it up. BUT, it worked for me, and it could very well work for you too!
OK, on the left, you see C4 (middle C) in Alto clef, and on the right, you see C5 (an octave above middle C) in treble clef. If you notice, they're almost in the exact same places on their respective staves. The treble clef C5 is just on the space, and the alto clef C4 is on the line. I kid you not, this is the method I used to know where notes were in both bass and treble clef until I started actually remembering where they were, and this device helped me to put the notes into memory. As an example, let's use the E on the bottom line of treble clef. The E an octave down would be in the space right below the alto clef staff. So basically, take the note you know in treble clef. If it's on a space, move it down to the closest line. If it's on a line, move it down to the space below it. This is where that note (albeit, an octave lower) falls on the alto clef. And it's the same thing for Bass=>Alto, except you move the note up rather than down.
You can also use this same method if you read tenor clef, but not alto. Although I'm not really sure what situation would call for only knowing how to read tenor clef. This is actually somewhat more simple than the transition between treble and alto or alto and bass. All you have to do is start with a note in tenor clef.
I do want to note, this method is supposed to be used for learning purposes only. If you find yourself several months or years from now still using this, then you haven't been committing to memory where the notes are.
The Range of the Alto Clef
This is the average range for music written in alto clef. Often, in viola music, if the note is above a high E, and multiple measures are in that high range, it will switch to treble clef until the notes return to the normal viola range. The low C, however, is a non-negotiable, at least for violas. Our notes can't get any lower, because that's our lowest open string. I do believe though, that regardless of instrument, that is the lowest note that exists in alto clef. One time, I had a director who wrote a note below low C into our part, and we had to tell him that we didn't have that note. Needless to say, he was a pretty clueless orchestra director. He was a trumpet player and although he was great at knowing how everything should sound, he really didn't know much about the technicalities of playing stringed instruments.
So, that's my basic how to about reading Alto clef! If you have any questions, feel free to ask them in the comments, as I would love to answer any anything you want to know! I'm also (hopefully) going to be doing a how to on other music theory things, such as reading other clefs. If you have any suggestions, leave them in the comments. If you want, you could even request some high-level theory stuff, because I probably know how to do it! Not tooting any horns, just trying to be helpful, as I am a college theory student with several years of theory experience under my belt! Hope to see you again soon!