Impromptu

Adjective

 * 1) Improvised; without prior preparation; extemporaneous; unplanned.

Noun

 * 1)  a short musical composition for an informal occasion often with the character of improvisation and usually to be played solo.

Adverbs for Impromptu
awkwardly; obviously; delightfully; en-chantingly; diffidently; undisguisedly; spontaneously; gracefully; altogether; evidently; warmly;  cordially;   sincerely;   wholly; charmingly.

Thesaurus
ad lib, ad libitum, ad-lib, ad-libbing, arrangement, at short notice, at sight, by ear, cadenza, caught napping, caught off balance, caught short, extemporaneous, extemporaneously, extemporaneousness, extemporarily, extemporariness, extemporary, extempore, extemporization, extemporized, flourish, haphazard, hasty, hot lick, improvisation, improvisatorial, improvise, improvised, improvision, improviso, interpolation, jury-rig, jury-rigged, lick, makeshift, measure, off the cuff, off the hip, off-the-cuff, offhand, on sight, out of hand, playing by ear, precipitate, pro tempore, quick, riff, rough-and-ready, snap, stopgap, surprised, taken aback, taken by surprise, taken unawares, temporary arrangement, temporary measure, tripped up, unarranged, unbegun, unconcocted, uncontrived, undeliberated, undevised, unhatched, unmade, unmanufactured, unorganized, unplanned, unpremeditated, unprepared, unprimed, unready, unrehearsed, unstudied, vamp