Ears forward, alert
Interested and paying attention — good sign, keep going
Ears flat / rotated back
Uncomfortable or annoyed — stop or try a different sound
Slow blink at you
Trust and affection — slow-blink back at them!
Tail straight up
Happy, confident greeting — they like what they hear
Tail puffed / tucked
Startled or stressed — reduce volume, try purr sounds
Head tilt
Curious, trying to locate/understand the sound
Approaches the speaker
Wants to investigate — let them sniff and explore
Walks away
Not interested right now — try again later, don't force it