What is another word for "improviso"?

Roget's Thesaurus (1911) lists these synonyms for "improviso": comes, creature, extemporaneous, extempore, extemporize, flash, impromptu, improvisate, improvisation, improvisatore, improvisatory, improvise, impulse, impulsive, indeliberate, inspiration, instinctive, mind, moment, natural, occasion, offhand, say, snap, spontaneous, spur, spurt, sudden, the, thought, uppermost, voluntary, what.