Comparisons
Thumb glissando--achieving a perfect legato by using the tip and the base of the thumb as though they were two different fingers--uses much motion and wide playing surfaces. As the base of the thumb plays the end of a key, the entire hand moves, raising the risk of striking other keys. Perfect legato may be difficult.
However, thumb glissando extends the reach of the hand as though a sixth finger were present. A confident, well-executed thumb glissando may be more efficient than a substitution, and can often be used where a substitution would be difficult or impossible.
Use thumb glissando only if direct fingering, redistribution, crossing, or finger glissando are impossible. If other factors are equal, the choice of thumb glissando or substitution is primarily a matter of the organist's skill in either technique.
