Abstract: Method and apparatus for securing vibrato and tremolo effects in musical instruments, such as electronic organs, wherein an incoming electrical signal is separated into high and low frequency components which are injected into opposite ends of a multiple-tap delay line. Analog multiplexers are connected to the line and are addressed to scan the delay line terminals sequentially in both directions. In a preferred embodiment, the duty cycles of high frequency sampling signals connected to enable the output of each multiplexer are modulated to secure a smooth transition in a composite output signal between the signals appearing at successive delay line terminals. Alternative methods and apparatus for blending successively scanned delay line signals are also disclosed.