Right phonetic
加 — supplies the sound exactly (jiā). Originally
力 strength +
口 mouth, meaning 'to boost with words.' In
伽 the phonetic is purely sound-borrow with no meaning carry-over; this is a transliteration character used for foreign syllables. Same phonetic anchors
咖 (coffee),
茄 (eggplant),
痂 (scab),
枷 (cangue) — most are also transliteration or rare lexical uses.