According to The Antique Sound Workshop’s “Guide to Recorders”:
Renaissance recorders have wide cylindrical or slightly tapered bores with a choke toward the foot and large single tone holes, produce a full, rich tone in the lower and middle registers. The earliest modern reproductions of these instruments achieved only a limited range of an octave and a sixth; more recent attempts to reproduce these instruments, particularly the Mollenhauer Kynsecker renaissance series, have successfully expanded the range to over two octaves. The extreme high register in these instruments, while quite playable, is nevertheless not as secure as on modern recorders and some experience on the part of the player is necessary to control the response accurately.
Baroque recorders, in comparison to the earlier renaissance-type recorders in use until the mid-seventeenth century, have much narrower, more sharply conical bores, smaller tone holes, and extremely narrow, highly arched windways. The tone of these instruments is relatively quiet, usually quite reedy and complex, and varies in timbre and volume from the low through the middle and high registers. They are extremely sensitive to subtle articulation and develop highly individual characters. They are excellent solo instruments, contrasting greatly with other baroque woodwind, string, or keyboard instruments, but are not well-suited to recorder consort playing because of their individuality and lack of blending properties. The alto recorder was the predominant size in this period, and the other sizes were used only occasionally. Most advanced players own and treasure one or more baroque solo alto recorders for the authentic performance of the sonata and concerto repertoire of the early eighteenth century.
Finally, modern recorders are extremely diverse in tone and playing qualities, but it is possible to draw a few generalizations about them: they tend to be fuller in tone than baroque recorders, although not as loud as renaissance recorders; their tone quality may range from full and warm through open and clear to bright and reedy, but is invariably plainer and less complex than historical recorders; they have relatively larger windways, sometimes with some curvature but usually straight, and usually have less resistance; they are not as sensitive to articulation, have a more limited dynamic range, and are not as stable in pitch. On the other hand, they may be played for longer periods of time and are far less prone to clogging if correctly designed and voiced, and they do not require as much care and attention. Perhaps most important, they require less effort and control on the part of the player and tend to be far more forgiving of a wide spectrum of playing techniques and styles. Whereas historical recorders are more player-dependent and require considerable experience and skill to produce optimum results, modern recorders have more of the performance built into the instrument, are therefore more reliable and less dependent on the ability of the player. Most modern recorders are equally suited to both ensemble and solo use; they are the ideal instrument for a player who does not want to acquire a number of highly specialized literature-specific reproduction instruments for early music but rather one all-purpose recorder which can be used successfully for all literature.
The full article is available at http://www.aswltd.com/guiderec.htm
Tom