[just_gjp]

Hello everybody,
I need a help finding a chemical element or combination that would change the voice (excluding helium or argon). Do you have any idea what elements could change the voice? The best if it would be some cheaper and maybe not gaseous element or combination, but i would prefer to get to know all the ideas and suggestions you have.

[Borek]

Voice change is not because of "an element" used, but because of the change of the density of the gas used for the sound generation. That means there are not many options possible, as you need a gas that is safe to use - first of all non toxic and non corrosive.

[Arkcon]

You've really already got the only two "safe", "effective" options available: helium and argon.  And I put both words in quotes for a reason. 

Although the much lesser density of helium raises the pitch of your voice, I've never heard someone on argon with a deeper voice.  I always assumed it would work, but no one has ever confirmed it for me. 

As to safety, the gas people use to inflate party balloons isn't pure helium.  There's plenty of air, and just enough helium to add buoyancy.  Pure helium is too expensive to use for party balloons.  So that's why its safe to breathe.  I don't know who mixes air with argon into a safe and effective voice modulator, or if argon's density make it dangerous to breathe in any mix.

[just_gjp]

Argon gas has really got the effect of deep voice. But i am trying to find some more gases or mixtures that would change the voice but not be harmful for health. My intention is not to use pure gas, but infuse it with some drink so neither helium nor argon gas would be harmful in small quantities.

[Borek]

Small quantities mean the effect is negligible. Besides, the use of heavier gases - even if they are inert - is dangerous, as they tend to stay in lungs and can induce asphyxia. Look for youtube videos with sulfur hexafluroide.

[Enthalpy]

[...] infuse it with some drink [...]

That part doesn't look good. You need a high proportion of gas in the lungs, not a little bit in the stomach.

Inhaled SF₆ has this effect but I doubt it's safe to insist with it.