I think any conductive wire can send and receive variable wavelength. A radio antenna and speaker wire etc.
At audio frequencies, any wire will work. (And, if have a piano hooked to your speakers, and the wire under tension and you pluck it or strike it to make a sound, that will have no effect on the sound coming through the speaker... Mechanically vibrating the wire will have no effect on the electrical signals through it.)
Piano wire is not insulated, so you'd have to be careful not to short it out (which would kill the sound and maybe fry your amplifier).
Piano wire is steel, which has higher resistance than copper. But with short lengths (such as in your living room) the resistance wouldn't be significant.
At higher impedance (such as with a guitar output, or a line-level connection between your DVD player and receiver) noise pickup is an issue, and coaxial shielded cable is normally used.
At radio frequencies (antennas, etc.) the inductance and capacitance of the cable becomes significant. Antenna and cable TV cables are usually rated at 50 Ohms, and that's because of the inductance & capacitance. If you use that type of cable with a speaker (at audio frequencies), it acts just like normal wire (with almost no resistance).
But I see the speaker with two wire connections could receive sound signal, and +,- doesn't matter to make a sound.
Electrons flow through the wire, and they won't flow if there's a break in the wire. You need a "complete circuit", which means the electricity flows through one wire, through the speaker, and back to the source.
You need two wires to make a complete circuit... If you disconnect the + or - connection to your car battery, your car won't start...
Audio signals are AC (current rapidly reverses direction depending on the frequency). So, there isn't really a positive and negative connection. If you have one speaker and you reverse the connections you won't hear a difference.
However if you have a pair of stereo speakers and you reverse one of them, one speaker will be pushing-out while the other pulls-in... With the vibrations and sound waves out-of-phase, you'll hear a loss of bass (as the bass frequencies are canceled) and you'll get a weird "phasey-spacey" sound. That's why speakers are marked + and -. So that two (or more) speakers can work together.
I have a lack of knowledge in electricity and radio wavelengths, I would like to clarify these..
Wavelength is related to frequency and speed. (If you don't know what frequency is, look that up before researching wavelength).
Electricity travels through wires at approximately the speed of light and audio signal wavelengths are miles long. Radio frequency wavelengths are much shorter.
Sound in the air travels at about 700 miles per hour (or about 1000 feet per second) so a 1KHz sound wave has an acoustic wavelength of about 1 foot. A 100 Hz sound wave in air has a wavelength of about 10 feet.