A number of features are quintessential to psychedelic music. Exotic instrumentation, with a particular fondness for the sitar and tabla are common. Songs often have more disjunctive song structures, key and time signature changes, modal melodies and drones than contemporary pop music. Surreal, whimsical, esoterically or literary-inspired lyrics are often used. There is often a strong emphasis on extended instrumental segments or jams. There is a strong keyboard presence, in the 1960s especially, using electronic organs, harpsichords, or the Mellotron, an early tape-driven 'sampler' keyboard.