The Sims 2/Electronics/Audio

With audio devices (stereos and wall speakers), your Sims can dance to music, as well as work out. More expensive stereos provide more fun, as well as a bigger score on the Environment.

Use the Turn On interaction to play some music. The Switch To interaction allows you to change to another station. The default station when you first turn any stereo on is the Salsa station. The other stations include Pop, Metal, R&B, and Techno. Unlike TV stations, certain age groups aren't attracted or repulsed by certain music stations. The type of music doesn't have any impact on your Sim's Fun need. To change the song currently playing, select Next Song. To turn off the stereo, simply use the Turn Off interaction. Any Sims who are still dancing to the stereo will stop.

Sims can dance to stereos, either alone or with others. If Sims Dance Solo, they gain Fun. Other Sims can join them dancing, but they won't gain any Social. To have Fun dancing as well as Social, your Sims must specifically use the Dance Together interaction on another Sim. This interaction being accepted or rejected depends on the Sims' Relationship score. Note that Dance Solo does not build the hidden Dance skill. To join other Sims who are already dancing, select the stereo or a dancing Sim and select Join.

As well as dancing to music, Sims can also work out to a stereo. They will change into their Athletic outfit and do floor exercises, which builds the Body skill. It works similar to the Work Out interaction with TVs.

Sims can also Listen to Music, but only if they're relaxing on a bed with the stereo in the same room.

As with all electronics, stereos break down, needing your Sims to Repair them, which builds the Mechanical skill.

Neukum Systems Wall Speaker
This isn't really a stereo, but a wall speaker. It acts as an extension to stereos, so you can place it in another room, as music playing on stereos are limited to the room they are in. This means you can dance to music anywhere on the lot. You cannot directly interact with the wall speaker, only the stereo it's linked to, so all interactions must go through the stereo, such as turning it on/off, dancing, etc.