Musical instruments are the backbone of any band, orchestra or rowdy event. They come in all shapes, sizes, and forms. Many instruments are electric, but not all are: depending on the instrument type, it might use older lever mechanisms or other sources of noisemaking. The age of an instrument's components, from a technological standpoint, is one factor to consider in musical instrument purchases. Older instruments are not necessarily worse, but the sound they create will almost always be different. This is particularly true of used or refurbished instruments, but it's true of mint-condition instruments from different decades, too. The best reviews will include information about this. Weight is a significant consideration for all instruments, for shipping costs if not for use. For handheld instruments in particular it's useful to compare their weights and dimensions to make sure that they'll be comfortable to use. Musical instruments are not generally custom-fit to each user, but the best instruments suit their users' mouth or hand sizes. Finally, power source (if applicable) and care requirements can matter for many instruments, such as portable guitars or harmonicas. Some instruments may use batteries of different sorts, while others will always require an amp and grid power to operate. Within the same category of instrument, a different model can also have different care demands, which reviews will often discuss: an older piano will often require more cleaning than a modernized keyboard, for example, even if they can be used for some of the same performances.