Like with Pokémon Black & White, Pokémon Black 2 & White 2 feature various changes to the background music.
Seasonal Changes
As the seasons change every month, almost all areas have slight changes brought on by the change in seasons. They start off with the basics in Spring but get additional features during certain months. Most notably is a chime in Winter in most areas. Below is a table of changes to the music in each area based upon the seasons;
Area Range
Spring
Summer
Autumn
Winter
Route 2 to Skyarrow Bridge
Flute
Louder arrangement
Piano Addition
Chimes in Intro
Route 4 onwards
Basic
Louder Arrangement
Xylophone Addition
Chimes
Route 12 onwards
Basic
Saxophone added
Piano Addition
Chimes
Undella Town
Quiet Music
Steel Drums Tropical Beat
Quiet Music
Quiet Music
Route 19, 20
Xylophone Addition
Steel Drums Tropical Beat
Violin Addition
Chimes
Route 21 onwards
Basic
Upbeat syntho
Violin Addition
Trombone
Movement-Based Changes
In some areas, the music is a static music style, but does in fact change when you make steps, adding to the beat while you move around the route
In a variety of places around Unova, there are various characters playing musical instruments. These characters add their instruments to the music of the area. Some are only active while you're within earshot while others are active non stop after you talk to them.
Area
Instrument Addition
Duration
Screenshot
Nacrene City - Café Warehouse
Accordion
After talking to the characters - When within earshot
Icirrus City - By the Gym
Claps
When within earshot
Opelucid City - By the Pokémon Centre
Keytar
After talking to the characters - When within earshot (Black Only)
Opelucid City - By the Pokémon Centre
Erhu
After talking to the characters - When within earshot (White Only)
Village Bridge - Top Left by Vending Machine
Guitar
After speaking to Aickman
Village Bridge - Bottom by bridge
Vocals
After speaking to Koontz
Village Bridge - On the bridge
Voice Percussion
After speaking to Russo
Village Bridge - In the top-right field
Whistle
After speaking to Derleth
Anville Town - On Bridge
Flute
After talking to the characters - When within earshot
Virbank City
Band
As you go deeper into the Gym, the music gets louder. Defeat the band members and the music loses instruments
Cave Changes
Next, there are changes in the various caves such as Chargestone Cave and Twist Mountain. As you get into the lower levels of the caves, the music will slow and the notes will get lower to help signify how far you are from the first floor. This isn't noticiable when on your bike and some caves such as Victory Road do not have this feature.
Icirrus City Changes
During the Winter in Icirrus City, you'll be able to access the house where one of the sound designers dwells. In this house, he'll gladly change the music while in the room to the music that played in Route 10 in Pokémon Black & White.