Tar. This is a Persian lute-like instrument that has spread all over the Caucasus region. Predictably, there is little classical music concertante repertoire for this uncommon instrument, but I have found one: the concerto by composer Khanmamedov from Azerbaijan. It is played by Ramiz Gulyev and the Azerbaijan State Symphony Orchestra under Adigozalov on a Boonloom CD.
 Electric guitar. Actually two guitars or the price of one. The electric guitar has not penetrated the classical market to a large extent, and the only concerto in my collection is the one by Terje Rypdal, which is actually for two of these instruments. It is played by Terje Rypdal and Ronni Le Tekro as soloists and the Riga Festival Orchestra under Sne on an ECM CD.
 Tap dancer. Seriously, this is not an April Fool's post, like the tuned clogs concerto I pulled off some years ago. There has actually been a composer of reasonable standing who has composed a concerto for tap dancer and orchestra: Morton Gould. A curiosity rather than brilliant music, but fun to listen to (and even more to watch as well). I have a recording by Lane Alexander and the Czech National Symphony Orchestra under Paul Freeman on an Albany CD.
 Birds. The use of pre-recorded bird song in classical music goes back to Respighi, who used a turntable with recorded nightingale sounds in his symphonic poem Pini di Roma. Contemporary Finnish grandmaster Einojuhani Rautavaara composed his Cantus Articus, subtitled Concerto for Birds and Orchestra, in 1972. The three movements feature tape recordings of birdsong collected near the Arctic Circle and on the bogs of Liminka in Finland. It is played by the Royal Scottish National Orchestra under Lintu, on a Naxos CD.
 Koto. This is the national instrument of Japan, akin to the Chinese zheng. A koto usually has 13 strings that are strung over 13 movable bridges, but versions with 20 strings are used as well. I recently came across one of the rare concertos for this instrument, by Daron Hagen. His 2011 composition Genji is a 28 minutes concerto for 20-string koto and orchestra in five parts. My version is by Yumi Kurosawa and the Orchestra of the Swan under David Curtis, on an MSR CD.