One of the easiest ways to set the mood of your adventure is to provide ambient background music. Trotting through the magical forest, play some magical sounding music. Exploring a mysterious cavern, play some mysterious sounding music. In a bustling town or busy tavern, play crowd ambience.
Switch the music from background to quicker-paced exciting music when a battle occurs to add to the tension.
Just remember the goal is to enhance the table top experience, not distract from it - so keep the volume of the music low so it is just ambient.
Sound effects
Another way to add to the fun factor is to create some specific sounds for monsters or phrases for major Non-Player Characters (NPCs) to play at appropriate moments.
AudioPet Bluetooth speakers
The best low-cost, high value bluetooth speakers I have found are the AudioPet speakers. They are tiny, but have great sound, good volume, are super easy to use, child safe, and on top of that they come in fantasy themes!
I love Scales the Dragon and Unichord the Unicorn, but there are a ton to choose from.
The bluetooth speakers pair up to any smart phone, device or pc, AND they pair together with other AudioPet speakers so you can use two or more speakers to spread the sound around the table.
On your smart phone you can use a multitude of music apps, but choose one that can repeat music automatically.
I would suggest NOT using Youtube or internet-based music apps unless you must because constantly stopping play to restart the music is distracting.
Warning: Tabletop killer
As soon as the table is quiet while you are fiddling with a device, everyone else takes this as an opportunity to pull out their phone. So get your AudioPet speakers setup on your smart phone before folks show up (test them). Once you have set them up the first time, you can connect them just by holding the power button on the bottom of the speaker. If you have two speakers, you power on the first (wait for the connected sound) and then power on the second and they will automatically connect to each other. The batteries last about 4 hours, so have the USB power cords handy to charge them up or use one speaker at a time and switch them when one battery runs down so you don't miss a beat (pun intended).
Frostbit Dragon Games Soundscape App
Our fantasy adventures come with a download code to download a special Soundscape App (for iOS or Android devices) that provides background music and sound effects that match the adventure allowing GMs to switch between the music and sound effects quickly with only a moments distraction.