Macro audio_node 

macro_rules! audio_node {
    (
        $(#[$meta:meta])*
        source $name:ident<$T:ident: $crate::math::Transcendental, const $BUF:ident: usize>
        $(where $($bounds:tt)*)?
        { $($tt:tt)* }
    ) => { ... };
    (
        $(#[$meta:meta])*
        processor $name:ident<$T:ident: $crate::math::Transcendental, const $BUF:ident: usize>
        $(where $($bounds:tt)*)?
        { $($tt:tt)* }
    ) => { ... };
    (
        $(#[$meta:meta])*
        sink $name:ident<$T:ident: $crate::math::Transcendental, const $BUF:ident: usize>
        $(where $($bounds:tt)*)?
        { $($tt:tt)* }
    ) => { ... };
}

Общий макрос для создания любого типа узла