Starfield Vocalist doubles the triggered abilities your permanents produce because something enters the battlefield. Creature-entry value, artifact-entry rewards, and landfall can all benefit when their trigger conditions are met. A deck with several such engines can get much more from one new permanent without needing to copy the permanent itself.
Mulldrifter can draw additional cards from its entry trigger, while a land entering can produce an extra Lotus Cobra trigger. Simulacrum Synthesizer can create more Constructs from a qualifying artifact. The Vocalist works with triggered abilities, not replacement effects, so it does not simply double the counters on a creature that enters with counters.
Warp lets you pay two mana for a temporary visit from your hand. That can set up a turn with several valuable entries, after which the Vocalist is exiled at the next end step. On a later turn you may cast it from exile, paying the applicable cost; warp does not give a free return. Casting it normally provides the ongoing engine immediately without that planned exile.
The cheaper mode is most useful when you already have follow-up plays ready. Spending two mana on the Vocalist and passing without an entry payoff wastes much of the temporary opportunity. In a blink or permanent-heavy value deck, its full-cost version can instead sit behind the board and improve successive turns. Build around effects you want to repeat, and keep the distinction between an additional trigger and a copied spell clear when planning the sequence.
