each titled (Concerto for little flute) with the additional note (The instruments transpose by a fourth) in RV 443 and (The instruments lower by a fourth) in RV 445. The three concertos RV 443, 444, and 445 are notated in C major, C major and A minor respectively. Also of note is the occasional use of notes outside the normal two octave compass of the recorder: the range of the solo sections is two octaves from notated F4 to notated F6, however there is a single notated C4 in the first movement of RV 444, a notated E4 in a tutti section in the first movement of RV 443 and low E4 in multiple tutti sections of RV 445. A number of possible have been proposed as the instrument intended for the performance of these concertos. The first suggestion was the use of the one keyed piccolo, or another small transverse flute, however such instruments had fallen out of use in Venice by the generally accepted time of composition of these concertos in the 1720s, and this opinion is no longer considered well supported. Another suggestion, first proposed by Peter Thalheimer, is the "French" flageolet (see Flageolets below) in G5, which was notated in D4, appearing a fourth lower, possibly explaining the note in the margins of RV 443 and RV 445 () and supported by Bismantova (1677 rev. 1694) and Bonanni (1722) which equate to the flageolet. However this suggestion has been opposed by the presence of notated F and F which are not within the typical compass of the flageolet, although they may be produced through the covering of the bell, sometimes combined with underblowing, as attested by theorists as early as Cardano (c. 1546) and as late as Bellay (c. 1800). Two instruments are conventionally accepted today for the performance of these concertos, the sopranino recorder, notated like an alto but sounding an octave higher, and the soprano recorder, following the instruction to transpose the parts down by a fourth. Winfried Michel was first to argue in favour of the soprano recorder in 1983, when he proposed to take Vivaldi at his word and transpose the string parts down a fourth and play the part on a soprano recorder in C5 (also "fifth-flute") using the English practice of notating such flutes as transposing instruments using the fingerings of an alto recorder. Michel notes that this transposition allows