Article: Lots of tone-generating devices and e-tuners are available that you can use quickly and in a pinch to get your guitar in tune. One of the most effective tuners available is the basic tuner available in the Apple app store. It's super cheap and super accurate. As long as your phone has juice in it, you can tune your guitar. . You don't always have to tune your strings the same old way. Famous guitar players like Jimmy Page, Keith Richards, and John Fahey frequently used alternate tunings to play their best-known songs, and alternate tunings are great for playing Delta blues or slide guitar styles. Some guitar players like to tune the bottom string to D, rather than E, making it easier to play certain chords and some styles of music. This is called Drop-D tuning. Other common alternate tunings include:  Irish tuning (DADGAD) Open C tuning (CGCGCE) Open D tuning (DADF#AD Open G tuning (DGDGBD)
What is a summary of what this article is about?
Look for free online tuners and apps. Use alternate tunings on an acoustic guitar