A variation of this fountain incorporates a worm-and-pinion gear, while another variation features double-action alternation. The book also describes a fountain with variable discharge. The book also describes fountains that change shapes at intervals. Mechanical musical machines The Banu Musa invented an early mechanical musical instrument, in this case a hydropowered organ which played interchangeable cylinders automatically. According to Charles B. Fowler, this "cylinder with raised pins on the surface remained the basic device to produce and reproduce music mechanically until the second half of the nineteenth century." The Banu Musa also invented an automatic flute player which may have been the first programmable machine. The flute sounds were produced through hot steam and the user could adjust the device to various patterns so that they could get various sounds from it. Practical tools The mechanical grab, specifically the clamshell grab, is an original invention by the Banu Musa brothers that does not appear in any earlier Greek works. The grab they described was used to extract objects from underwater, and recover objects from the beds of streams. The Banu Musa also described bellows that could remove foul air from wells. They explained that these instruments allow a worker to "descend into any well he wishes for a while and he will not fear it, nor will it harm him, if God wills may he be exalted." Water dispensers The book describes a dispenser for hot and cold water, where the two outlets alternate, one discharging cold water and the other hot, then vice versa repeatedly. It also describes a vessel with a basin by its side where, when cold water is poured into the top of the vessel, it discharges from the mouth of a figure into the basin; when hot water or another liquid is poured into the basin, the same quantity of cold water is discharged from the mouth of the figure. The book also describes a boiler with a tap to access hot water. The water is heated through cold water being poured into a pipe which leads to a tank at the bottom of the boiler, where the water is heated with fire. A person can then access hot water from the boiler through a tap. Other devices Some of the other devices the Banu Musa described in their book include: Mechanical trick devices Hurricane lamp Self-trimming lamp (by Ahmad ibn Mūsā ibn Shākir) Self-feeding