Sourceval create : ?seconds:float -> ?tracks:int -> unit -> t Sourceval set_head : t -> float -> unit Sourceval set_speed : t -> float -> unit Sourceval record : t -> int -> unit Sourceval recording : t -> int option Sourceval set_level : t -> int -> float -> unit Sourceval set_loop : t -> (int * int) option -> unit Sourceval lift : t -> int -> from:int -> until:int -> unit