pipe up

Short definition from Wiktionary

Verb

1. 1
   To speak up, especially in a robust, assertive manner; to say something loudly and suddenly.
2. 2
   To begin singing or playing musical notes on a pipe or similar wind instrument.
3. 3
   To begin to blow more vigorously.
4. 4
   To call, awaken, or summon, as with a musical instrument.