Correction: Op. 40 is an organ sonata; piano concerto no. 1 is without op. no. Eric 00:40, 28 October 2009 (UTC)
I think I may have been confused and that it is the organ sonata, sometimes listed variously as op posth., op. 40, and op. 45 (the latter two conflicting with other works), that is without opus no., but I'll check further! Eric 22:20, 4 November 2009 (UTC)