Sing your heart out. They love it as it's the human element in the sea of synthesis. It connects on that human level. People don't 'sing' instrumentals, there's just not much emotional connection to them. Net result is that most instrumentals on an arranger, unless the player is exceptional, are going to register closer to elevator music more than anything else.

Instrumentals have their place but are mainly for background. Vocals put the 'you' out there.