I've been playing my guitar or mandolin along to various recordings and I'm wondering if some musicians tune down or up from standard or true pitch so as to get the same sound with an easier to make or play chord.For example,tune the guitar strings down ,then play an easier to make G and C chord instead of an awkward F and B flat.I know the old capo is available for guitar,so this may be more relevant to the mandolin. I swear I listen to some celtic stuff thatis in D or G,but if my mando is tuned up to "correct",same as the piano,pitch.the tune will demand an F chord and the tune is in F. Can someone clarify and make sense of this? Thanks.