Which of these musical forms is the odd one out?

What is the correct term for music created spontaneously when a player, most typically of a keyboard or other harmonic instrument (maybe the harp or guitar), 'fills in' by making it up as they go along?

Which instrument comes in variants including the concert, Celtic, cross-strung and chromatic?

Paul von Janko, in the 1880s, proposed a technical standardisation that could make life far simpler for vast numbers of musicians, but it did not gain popularity. What was it?

Those sad souls who only recognise one organ piece, probably know this one as (and if they remember all of that right, they probably congratulate themselves on their erudition): it is of course that iconic pre-Gothic work which was arrestingly (if somewhat incongruously) used as the theme tune to the film , the one 'that goes: 'Da-da-dah ... ... ... da-da-da - dum - dum - DUM' ( )'. Which of the following points is still regarded as true about the origins of this piece?

Fairly closely related to the Impromptu is the Humoresque (a work title which seems something of a hostage to fortune: 'Buy this and play it, but you can't claim your money back if your audience fails to smile or laugh'!).Who wrote the widely-familiar example of this genre, which also became fairly widely wedded to a set of semi-scurrilous lyrics from the world of railway travel (a world with which the composer himself was reportedly obsessed), and which began as follows: ?

Many respected composers were nurtured on, or later absorbed and used, the folksongs of their native lands: Bela Bartok in Hungary, Ralph Vaughan Williams and several others in Britain; Canteloube with his enchanting and atmospheric , for instance. One of the pioneer activists in the British folksong movement was a man with a most splendidly appropriate name for this role: who was he?

Composers have always felt entitled to 'help themselves' from music happening around them in nature, the weather and human activity ~ birdsong, Chopin with his raindrops, Kenneth Alford with his March (reputedly starting with the two-tone whistle of this military gentleman before he took any shot on the golf course). Eric Coates in the 1930s wrote two Suites, the first of which starts with a movement depicting Covent Garden market, and which in turn incorporates a catchy, whistleable tune from an old London street-cry. Which is the title or catchphrase of this 'open-air commercial'?

Standard modern concert pitch is such that the A above middle C represents a frequency of 440Hz (cycles per second); Baroque pitch has been (at least retrospectively) standardised to equate with A♭ in this tuning. What, therefore, is the frequency of Concert A at Baroque pitch?

At the end of a musical event, British (and other English-speaking) audiences may request an from the artist/s: a piece performed again, or maybe something else appropriate to conclude the concert and bring everyone 'back down to earth' from whatever cultural and/or emotional heights they had been scaling together. Presumably it is felt duly sophisticated to use a foreign term to express this request. The French themselves do not use this term; what do they do or say instead, in the and elsewhere?