A grid, network, or crosshatch found in the eyepiece of various optical instruments to aid measurement or alignment
Tchaikovsky: Piano Concerto No. 1, Op. 23 - Anna Fedorova - Live Concert HD (YouTube) Pianist Anna Fedorova and the Nordwestdeutsche Philharmonie led by Yves Abel perform Tchaikovsky’s ‘Piano Concerto No. 1’ in The Royal Concertgebouw Amsterdam. The concert is part of the NPO Radio 4-series The Sunday Morning Concert.