Dan Grinstead of Seattle plays solo piano in the small worlds of ragtime and traditional jazz.   He is a well-known solo and duet ragtime performer who has played at all the important ragtime festivals in North America.   Grinstead has recorded solo ragtime CDs and a duet CD with Glenn Jenks entitled "Ragtime Bigtime."   In West Seattle he is a regular performer for vaudeville and silent movies.   Dan's interest in ragtime began in 1955 with sheet music, old records and player piano rolls.   He has a real job as a marine engineer.