I've been trying to pick up on certain elements of each of these 'different emotions of love' tunes to try and incorporate them into my own works... The only real ESSENTIAL thing they need seems to be vocals, it's very hard (but not impossible) to have a 'love song' without lyrics.
Other than that I've noticed these elements for these categories of 'love music'.
Romantic music to make you want to make love to your other half and smooch a lot -
Spanish Flamenco-style guitars are often used.
String Sections
Electronic Guitars (often 'ballad' style)
Minor Scales (would really like to know which, and which modes are often used!)
Vocal harmony
Pianos
Brushed Drum kits
Smooth pads
Subtle Percussion such as tambourines
Woodwind - Particularly Saxophones.
Sad love music that you often listen to when lonely, which makes you feel one hundred times worse
All very similar to the romantic elements just with more sad tones in voice and often slower swings etc.
And obviously there's plenty more types of love music, but I'm interested to see what everybody else has noticed... Please
