There are many different ways to match the right types of sounds to plays melodies to a particular style of music on your keyboard. Of course, rules are made to be broken, but here are some common practices and guidelines for matching styles and sounds.
Acoustic and electric pianos: Work well for pretty much everything except heavy metal, punk rock, grunge rock, and polka (you gotta have an accordion for that!).
Combo/tonewheel organ: Works well for pretty much everything and is the only keyboard sound likely to be accepted in heavy metal, punk rock, and grunge rock. Just use a more aggressive sound, not your jazz or skating sound.
Pipe or church organ: Works best for classical and liturgical/church music but can also be used sometimes in rock, progressive rock, and heavy metal music.
Solo brass and woodwinds: Work well for pop music, Broadway show tunes, jazz and big-band music, soul and R & B, Latin, folk, and new-age music. It’s also good for some classical and liturgical pieces.
Acoustic guitar: Works well for pop, country, new-age, folk, Latin (especially bossa novas and sambas), and some softer rock music. It’s also good for some classical and liturgical pieces.
Electric guitar: Depending on how clean or distorted your sound is, works well for pop, rock, country, new-age, soul and R & B, and jazz. Heavy distorted guitar works well for harder rock, heavy metal, punk rock, grunge rock, and annoying your neighbors. Especially if they play guitar.
Strings and string section: Works best for classical and liturgical music as well as Broadway show tunes. You can also use it for effective introductions to many styles of music before moving into a more keyboard-based sound.
Mallet sounds: Works for various styles depending on instrument. You can use vibraphone (vibes) for jazz and Broadway/big-band songs, while marimba, xylophone, and steel drum work nicely for island-tinged pop and folk music, reggae, and Latin music.
Synth sounds: Works well with a variety of styles. This category is pretty broad, but in general most dance music from the ’70s to today sounds better with synth sounds playing the melody rather than acoustic instruments. Many classic rock and progressive rock music features synth solos as well.
Classical music and holiday selections also adapt well to synthesizer sounds, be they keyboard-based pieces or orchestral adaptations. Think Wendy Carlos, Tomita, and Mannheim Steamroller.