Sheila Romeo explains that "[i]n theory, any chord from any mode of the scale of the piece is a potential modal interchange or borrowed chord. Some are used more frequently than others, while some almost never occur."13
In the minor mode, a common borrowed chord from the parallel major key is the Picardy third.
In the major mode, the most common examples of borrowed chords are those involving the ♭, also known as the lowered sixth scale degree. These chords are shown below, in the key of C major.14
The next most common involve the ♭ and ♭. These chords are shown below.15
Chord progressions may be constructed with borrowed chords, including two progressions common in rock music, I–♭VII–♭VI–♭VII, common everywhere, and I–♭VI–IV (Playⓘ), used by bands like Genesis, Yes, and Nirvana.16 ♭VII is from Mixolydian and ♭VI is found in both Aeolian and Phrygian.17 The ♭VII–I cadence with ♭VII substituting for V is common, as well as ♭II–I, ♭III–I, and ♭VI–I.18 In popular music, the major triads on the lowered third (♭III), sixth (♭VI) and seventh (♭VII) scale degrees are common.
Borrowed chords have typical inversions or common positions, for example iio6 and iiø65, and progress in the same manner as the diatonic chords they replace except for ♭VI, which progresses to V(7).19
Romeo, Sheila (1999). Complete Rock Keyboard Method: Mastering Rock Keyboard, p. 42. ISBN 0-88284-982-4. Bouchard, Joe and Romeo, Sheila (2007). The Total Rock Keyboardist, p. 120. Alfred Music. ISBN 9780739043127. /wiki/ISBN_(identifier) ↩
Benward & Saker (2009), p. 71. ↩
White, William Alfred (1911). Harmonic Part-writing, p. 42. Silver, Burdett, & Co. [ISBN unspecified]. https://archive.org/details/harmonicpartwri00whitgoog ↩
Kostka, Stefan; Payne, Dorothy (2004). Tonal Harmony (5th ed.). Boston: McGraw-Hill. p. 343. ISBN 0072852607. OCLC 51613969. 0072852607 ↩
Benward & Saker (2009), p. 74. ↩
Sorce, Richard (1995). Music Theory for the Music Professional, p. 332. Scarecrow Press. ISBN 9781461664208. /wiki/ISBN_(identifier) ↩
Kostka, p. 344. ↩
Kostka, pp. 346–347. ↩
Romeo (1999), p. 43. ↩