New sounds can be bought at the Bongos A Go-Go store at DK Town:

Barnyard: 1050 coins
Big Band: 88 coins
Car: 66 coins
Classical Orchestra: 2220 coins
Cold: 460 coins
Country: 49 coins
Dogs: 11 coins
Electrical Drum: 25000 coins
Jingle: 333 coins
Kirby: 2599 coins
Konga Crew: 64 coins
Laser Space: 77 coins
Latin Percussion: 1900 coins
Mario: 4599 coins
Quiz: 912 coins
Toy: 14900 coins
Whip It: 707 coins
Zelda: 4599 coins