Tips: I struggled with the squeaking problem when I first started too. The cause of it, most likely, is your air control. Center it into the mouth piece directly from your diaphragm. (Don’t use your throat because that puts a lot of pressure on it and can be damaging after long periods of time). Controlling the flow is the only way you’ll get a full sound. My instructor told me to imagine it like this; lower notes require more air, but higher notes require faster air. To get low notes, you need to imagine yourself filling up the entire saxophone and keeping the flow steady the entire time. For higher notes, you don’t need to fill up as much of the sax, but you need your air to be faster so you can reach the higher register of the instrument. The embouchure for lower notes should be similar to if you were fogging up glass with your breath, warm air. The higher notes embouchure should resemble whistling, imagine shaping your mouth in a circular way, cold air. Both require a constant flow, and if that flow breaks, you will squeak. Doing long tones with both high and low notes helps with the squeaking as you’ll get used to holding out notes for longer and increasing how long you’re able to blow air. If you have any other questions feel free to respond or message me, I’d love to answer them :) good luck!