Orthogonal frequency division multiplexing (OFDM) is a transmultiplex (TMUX) technique characterized by a low computational complexity and reduced inter-symbol/inter-carrier interference (ISI/ICI). Recently, new TMUX structures based on multicarrier modulation have been proposed aiming at even better performances. Such new structures include a cosine-modulated filter bank (CMFB) and a modified DFT filter bank (MDFTB). This work introduces design techniques for the CMFB and MDFTB structures with a large number of subbands (several hundreds or more), zero ISI, and small levels of ICI for most practical applications. The design is based on the concept of an Mth-band Nyquist filter, which inherently yields zero ISI and a highly selective filter bank, and in the FRM structure enabling one to synthesize FIR filters with a significantly reduced number of coefficients. The prototype example filter is optimized to minimize the resulting ICI. A design example is included to illustrate the benefits of the proposed technique in filter bank applications demanding a very large number of channels.