In this paper we introduce a new class of $K$-algebras associated with
quivers. Given any finite chain $\mathbf{K}_r: K=K_0\subseteq K_1\subseteq ...
\subseteq K_r$ of fields and a chain $\mathbf{E}_r : H_0\subset H_1\subset ...
\subset H_r=E^0$ of hereditary saturated subsets of the set of vertices $E^0$
of a quiver $E$, we build the mixed path algebra
$P_{\mathbf{K}_r}(E,\mathbf{H}_r)$, the mixed Leavitt path algebra
$L_{\mathbf{K}_r}(E,\mathbf{H}_r)$ and the mixed regular path algebra
$Q_{\mathbf{K}_r}(E,\mathbf{H}_r)$ and we show that they share many properties
with the unmixed species $P_K(E)$, $L_K(E)$ and $Q_K(E)$.