....a stream of ever changing surprises.
Some improvisers, my teacher was one, assert they are fully aware in advance of everything which is going to happen; every note is calculated.
Speaking of scholarly collections of data, I find that the word Improvisation is relatively new in the English language. Here is an overview from the vast collections of the historically based Oxford English Dictionary, 2 ed.:A. adv. Without preparation or premeditation; off-hand, on the spur of the moment; extempore.1669 LADY CHAWORTH in 12th Rep. Hist. MSS. Comm. App. v. 11 Mr. Elliot..desired Mr. Titus to make some verses..which he did thus, impromptu [etc.]. 1788 BURNS Let. to Mrs. Dunlop 16 Aug., She sometimes hits on a couplet or two impromptu. 1791 BOSWELL Johnson (1816) I. 31 note, This was made almost impromptu. 1882 FARRAR Early Chr. II. 375 note, This was afterwards improved into the story that he [John] wrote the whole Gospel impromptu.B. n. Something composed or uttered without preparation or premeditation; an extemporaneous composition or performance; an improvisation. Also, a musical composition having the character of an improvisation.1683 D. A. Art Converse 44 We must deal plainly and seriously with such men, waving all in promptu's and subtilities. 1693 DRYDEN Juvenal Introd. (1697) 37 They were made extempore, and were, as the French call them, Impromptus. 1776 JOHNSON Poem (title), To Mrs. Thrale, on her completing her thirty-fifth year, an impromptu. 1847 DISRAELI Tancred II. ix, Lady Constance..had a variety of conclusions on all social topics, which she threw forth..with the well-arranged air of an impromptu. 1880 GROVE Dict. Mus. I. 768/2 The two sets of pieces by Schubert known as Impromptus..were..not so entitled by him.C. adj.1. Composed or uttered without preparation or premeditation; improvised; invented, produced, etc. on the spur of the moment and without previous thought.1789 MRS. PIOZZI Journ. France I. 240 Who would risque the making impromptu poems at Paris? 1830 D"ISRAELI Chas. I, III. Pref. 4, I am not fortunate in impromptu replies. 1849 THACKERAY Lett. Apr., I daresay I shall have to make an impromptu speech.2. Made or done on the spur of the moment; hastily made for the occasion, or converted to use in an emergency; extemporized, makeshift.1764 MRS. HARRIS in Priv. Lett. Ld. Malmesbury I. 118 Lord North took an impromptu dinner with us yesterday. 1800 E. HERVEY Mourtray Fam. I. 67 They had a little impromptu ball. 1856 MISS MULOCK J. Halifax xxii. (1865) 215 My daughter encouraged me to pay this impromptu visit. 1872 BAKER Nile Tribut. viii. 128 We prepared an impromptu raft.Hence impromptu v., to compose off-hand; to improvise, extemporize. impromptuary a. = C. 1. impromptuist, one who composes off-hand, an improviser.1802 H. SWINBURNE in Courts Europe (1841) II. 334 The soldiers sing in the evening an endless German song, and the sailors impromptu in Danish. 1802-12 BENTHAM Ration. Judic. Evid. (1827) II. 2 Answers impromptuary. 1834 MEDWIN Angler in Wales I. 48 In a pelting rain, impromptu"d the following epigram. 1848 Athen�um 5 Aug. 773 Ballast-waggons..impromptued and filled up with seats. 1882 Chamb. Jrnl. 742/2 Theodore Hook..was a most prolific impromptuist. 1897 F. HALL in NationThe word Improvisation only appears toward the end of the 18th century, but it is equivalent to rthe earlier expression Impromptu, borrowed from French with same meaning. It is commonly used from the middle of the 17th c. on, and is much the same in usage as the Latin ex tempore. It is interesting that the copious OED does not have examples from the vibrant and experimental Elizabethan world, where the master wordsmith Shakespeare actually improvised some 2500 new words into the language. But lack of a term does not mean lack of an idea: Greeks and Romans had no word for our concept of ART, using techné and ars which are craft words, as sufficient for their well developed and artistic Arts.In the above OED citations, the word Improvisation is variously applied, first to a style of fluent speaking, also to the quick making up of rhymed couplets, further to songs of various sorts, and even to a surprise dinner menu. It is a highly variable word with many meanings, to which we can add more in these following areas:
......I've probably expressed myself quite badly, but never mind..
In both cases I would suggest that what emerges often gravitates towards a patchwork of figurations and ideas which are the most ingrained part of my keyboard vocabulary.