Singing soft doesn't have to mean communicating weakly. Getting this right can make the difference between a soft passage that no one pays attention to and one that subtly but surely sucks the air out of the room and demands attention!
First verses, breakdown choruses, light bridges, tags are some common places that can be more effective with softer dynamics. Confusing soft singing with meek, ineffective sound is actually something I hear all too often and is too important to leave uncorrected. Here are some ways to get powerful emotional responses from soft singing:
Don't drop your voice off the map...Good and interesting vocal dynamics require variety in volume intensity. However, level your intensity a bit... definitely back off loud notes, but also don't sing so soft or 'covered' (hollow, hooty) that you can't be heard, especially on low notes. Use tone variation -- communicate passion in all the notes and lyrics -- instead of huge volume swings. Your voice won't scare or lose your live performance listener, and it will also record much better.
Keep your articulation clear...Lowering vocal volume shouldn't lower your clarity. You can whisper and still draw the ear to you if you make sure to make the words are understandable.
Use the power of hushed intensity...This is something I learned as a jingle singer where everything we sang had to have memorable impact as well as surgical precision. Keep energy in your breath compression power source! Your soft tone needs to be supported and controlled. Singing soft is a kindred art to ballet, juggling, plate spinning, putting a golf ball... it looks so easy, but it takes real power to support the apparent effortlessness (quite the paradox, isn't it?)
Listen to playbackPut on the listener's hat. Do you hear yourself communicating or just keeping the message to yourself?
Remember: Soft singing is not for wimps! Come on... zing somebody!