Henley says:
"GAGLIANO, GIOVANNI (I) - Fourth son of Niccolo (I). Nephew and pupil of Gennaro. Worked at Naples, 1740-1806. Also a short time in Venice, about 1761. A few of his instruments are of unquestionable merit. Modelling treated with considerable mathematical and academic skill. Outline and arching somewhat Stradivarian, but curve of upper part never really fine. Scrolls typically illustrative of the small Gagliano style. Top wood often of wide grain, backs and ribs of lightly flamed material, scrolls sometimes of very plain wood. Mostly orange-brown varnish, also a brown of darker shade. Violinists have allowed their enthusiasm (with the sometimes exaggerated notion of the glamour of Italian tone, and possibly the imaginary assistance of the exorbitant prices given by connoisseurs and wealthy amateurs of enfeebled playing abilities who often prate and assert that a Gagliano is the most easily responsive of all instruments) to throw a captivating spirit over them. With such praise, we do not entirely disagree, if we regard the instruments as solely destined for chamber-music playing in small concert rooms but we emphatically declare them to be ill-adapted for the modern concerto as the tone lacks power, and though there is a certain penetrative quality, the vigorous player is apt to stifle its purity. Best specimens realized about £120 in 1925. Also made several instruments hurriedly and of careless handicraft. Players who pretend to an exemption from prejudice, will appreciate the futility of dipping deeply into their pockets for such productions though the alluring name of Gagliano may be within."
-William Henley, The Universal Dictionary of Violin and Bowmakers
Hamma says:
"GAGLIANO, Giovanni I (Joannes), Filius Nicolaus
The fourth son of Nicolas. His instruments have flat archings with broad edges, but are not always particularly careful in their choice of wood. The scrolls are unattractively carved with the flanges frequently overlong."
-Walter Hamma, Italian Violin Makers
