吉他变调夹是一种横向安置在吉他琴弦上用于提升其音调的设备。

变调夹最初的用途是调整吉他的音调，使其与演唱者的嗓音相协调。现在，它被广泛的用于弗拉门戈吉他、古典吉他及民谣吉他的演奏中。

用于独奏曲目时，变调夹常被置于第一到第四音品之间，其中被放置在第二品的频率最高。高于第四品的使用基本上只见于伴奏。

A capo (/ˈkeɪ.poʊ/ or /ˈkæ.poʊ/; short for capo d'astro, capo tasto or capotasto [kapoˈtasto], Italian for "head of fretboard"; Spanish, capodastro [ka.po'ðas.tɾo]) is a device used on the neck of a stringed (typically fretted) instrument to shorten the playable length of the strings, hence raising the pitch. It is frequently used on guitars, mandolins, and banjos. The word derives from the Italian "capotasto" which means the "nut" of a stringed instrument. The earliest known use of the term "capotasto" is by Giovanni Battista Doni who, in his Annotazioni of 1640, uses it to describe the nut of a viola da gamba. The first patented capo was designed by James Ashborn of Wolcottville, Connecticut, USA.