from typing import List
from typing import Counter


def get_base_freq(reads: List[str]):
    """
    Returns the aggregate frequency of bases in the sequencing reads
    >>> get_base_freq(["NAACGTTA"])
    Counter({'A': 3, 'T': 2, 'N': 1, 'C': 1, 'G': 1})
    >>> get_base_freq(["AACGTTA", "CGCGTTT"])
    Counter({'T': 5, 'A': 3, 'C': 3, 'G': 3})
    """
    concatenated_reads = "".join(reads)
    return Counter(concatenated_reads)