I've just started playing the clarinet.

Everything is fine until I hit the lower G. Sometimes I get it and sometimes
I don't. It seems as though I'm blowing against some blockage and I can't get
the note out. I made sure my fingering was correct and I wasn't accidently pressing
a wrong key, I change the way I hold the clarinet and the way I aim air at the
reed and I still can't figure out what's wrong. It works sometimes and sometimes
not. Help.

Hmm... Alright, make sure you've covered ALL holes. That is every hole the back (F) to low G, or all three bottom segment holes. I am assuming you are playing a Bb clarinet. It well help if you give a lot of air, you know, really loud, or if you get a running start of sorts, as in you start of at C or so and continue down at a slow to medium pace, particularly slurring the notes (just moving your fingers so that the notes change through the course of one constant string of air). If this does not work, just post here.

The frustrating thing is that sometimes I get it and sometimes I don't and I can't figure out what I'm doing diferrent. If I start at C and slur my way down to G I can sometimes
get it. I try to notice what I'm doing when I do (how I'm holding the instrument, aiming my
breath, etc. ) Then all of sudden I can't get it anymore. I blow but there seems to be
a blockage and the breath doesn't even get into the instrument. It's very frustrarting.
The fact that air doesn't go through makes me think of the reed, but I've changed that
several times.

I love practicing the clarinet and I'd like it to be my instrument but I'm stuck at this point and can't make progress.

Hi, I think you problem is your Clarinet is been lost air, in one of the holes.

To Check: disassemble clarinet pieces, then test blowing in one side, (closes holes with fingers) if escape air...

Thanks.

This could be that the link arm between the upper & lower joints is mis-aligned meaning that, unless you use a lot of pressure with RH 1st finger, the pad on the lower joint ring key isn't closing fully. Try rotating the joints so that the link is not engaged & try playing again. If things improve a quick adjustment by a techician will cure this.

Not to mention, you might consider adjusting your mouth on the reed. It might be because you have your lip too low, as in it is too far in your mouth. Lower notes are generally easy... so I would at least reccomend that you play slowly for songs with G in them, until you get it. It will come much easier with practice. Please keep in mind that you will most likely encounter similar problems with notes over the bar (high B natural and up).

Make sure all the holes are covered. Also use a lot of air and use your diaphragm.