I'm pre-T and started doing vocal exercises a year or two ago to see if I could deepen my voice and I was surprised by how quickly and how well they worked. I got most of them from searching online for vocal training used by singers so I can't remember all of them but I'll share the ones I can. It's probably worth noting that my voice has always been on the deeper side so your experience with the exercises may be different depending on what your own voice is like. Also, if you feel any pain in your neck or throat after doing them it's best to take a break so you don't strain your vocal cords. If you strain them too much, you'll have trouble holding any sort of tone because it'll cause your voice to keep cracking.
Longer and thicker vocal cords is what makes for a deeper voice. T will thicken your vocal cords but you can work on stretching them to make them longer without needing T.
Here's the first exercise:- Sit up and tilt your head as far forward as you can until your chin is touching your collarbone (or as close to your collarbone as you can get) then start humming.
- As you're humming, gradually lower your voice until it's as deep as it will go then slowly raise your head as you continue you to hum. Try keeping the same deep tone while your raise you head up to look at the ceiling.
- You'll probably notice that when you're looking up it's hard to hold a lower tone but that's normal, just keep humming as deeply as you can while you gradually lower your head again.
The trick is to repeat the exercise until you're able to hold that lower tone with your head up. Once you can, continue doing the exercise with deeper and deeper humming. It will slowly stretch your vocal cords and after a while, your voice will naturally be deeper.
Now the second exercise:- This one is pretty simple. Try speaking from your chest rather than from your throat. It's common for women to speak from their throats whereas men typically speak from their chest. That's why male voices resonate more deeply.
- Take a deep breath and as you exhale, expand your chest. Now repeat the same action but as you exhale, lower your voice as deeply as you can. You should be able to feel your voice resonating in your chest and in your vocal cords.
- Repeat the exercise a few more times and each time you do, try to "push" your hum down into your chest as you exhale.
- This will help you get used to speaking in a lower voice without having to move your throat each time to forcibly stretch your vocal cords.
And the third exercise:For this one you'll need a piano or keyboard. To simplify things I'll just explain how the exercise workds using the virtual one found here
http://www.virtualpiano.net/. (If it's against the TOS to post this link, I can remove it.)
- Start on the left side of the piano and find the A-22 key. Hit the key to play the note and try humming along to match your voice to the tone that's played (if you can't match the pitch exactly, that's okay just as long as the tone of your voice sounds close to the note being played).
- If A-22 was too low for you, try going up a key or two until you find a tone you're able to match with your voice.
- If your voice is naturally lower and A-22 was too high for you, keep going lower until you find the note that your voice naturally matches.
- Once you've found the note that best fits the sound of your voice, try playing a note lower. As you hum lower your voice to match the note but this time hold it for as long as you can. Repeat this step as you work your way down the scale into the lower registers.
This is just another way of stretching your vocal cords and it will give you an ear for exactly how low your voice is compared to how low you want it to be so that you can work on deepening it a little each time.
As for taking T supplements to lower your voice, I don't think they would help. Usually supplements that boost T only work if the body is already actively producing T itself and even then, most of them still don't work. Just keep at the exercises though and they'll definitely help. If I can remember anymore, I'll post those too. I'm sure there are plenty of voice deepening exercises you can find online too. One of the last (and cheesiest) exercises I used to do was just singing a lot to music where the singer had a deeper voice. That can be tricky though because it's easy to strain yourself that way so it's fun but I would try that last.