This paper presents a hybrid adaptive multi-carrier architecture that, according to the channel condition, wisely switches between Orthogonal Frequency Division Multiplexing (OFDM) and orthogonal Filtered MultiTone (FMT) modulations. This new scheme is referred to as hybrid-FMT (H-FMT). For H-FMT, the problem of jointly allocating the sub-channels powers, the overhead duration, and the modulation scheme, to the channel condition to maximize the achievable rate, or minimize the total transmitted power, is considered. Furthermore, the authors present an efficient implementation that requires minimal increased complexity w.r.t. baseline OFDM. The potential benefits given by the adoption of H-FMT are shown through extensive numerical results over typical WLAN channels.