Once you have determined the range in which the solo is written and have established a pitch foundation, decide on its volume.
Solos of the HIGHEST VOLUME are required when the desired dynamic level of the solo is fortissimo or above, and in accompanying jubilant hymns when the solo must be heard by the singing congregation over the rest of the organ.
FIRM BUT LESS ASSERTIVE solos are called for when the desired dynamic level of the solo is about forte, and in accompanying more meditative hymns with a solo combination.
SOFTER solos can be used when the dynamic level of the solo is up to a mezzo-forte, but cannot usually offer enough support for a singing congregation.